One consistent point I've consciously tried to stress in the campaigns I run is to give the PCs underlings, or minions.
What do I mean by minions? Well, basically the same thing that's meant when used by the various adversaries of the campaign; low-level characters in their employ or otherwise bound to their will, and if not always perfectly competent, with sufficient loyalty to be left alone to do their best to accomplish their leader's goals.
Why minions? A bunch of reasons.
First, PCs are exceptional. Even in systems where PCs start at low level and don't have cosmic power, having a few people who are meant to stand in as baseline individuals lets you emphasize how, even if the PCs aren't superhuman (yet!), they are still a cut above, by giving them a man-at-arms who does his best, but lacks the infinite drive and indifference to hardships that PCs effortlessly display.
Secondly, it lets you handle the small stuff. At the level where PCs can be assumed to handle a particular kind of challenge without risk, they should be able to have their people handle the challenge for them. It explains why the PCs are not wasting screen-time with whatever the challenge is most of the time while still bringing in a reason to deal with the challenge if things so suddenly wrong, and in so doing, you make that kind of encounter interesting.
It also lets you introduce needed capacity in terms of allies more gracefully. If the campaign really expects that you have a cleric as healer and condition-remover and no one is interested in playing that role, then it's a lot simpler to introduce an NPC cleric ally as buffered by the PC's entourage than just dropping them into the party proper. Also, having an entourage of NPCs with defined histories and skillsets makes it a lot easier to drop a needed clue or direction on the party when needed, and always lets you provide a bunch of different perspectives on a creature or event in the game world to let the PCs come to their own conclusions.
While minions should always be a net benefit to the party, you can also use them tactically in specific situations to help drive the plot in certain directions. A small group of PCs can probably live off the land in the deep wilderness indefinitely; if the party have a druid and are willing to say "Sure, let's just not stop off in any towns at all as we cross Occupied Kingdom. Showers and beds are overrated!", then they can avoid a lot of plot hooks. And it gets worse when the party wizard gets Teleport in a few levels. But by giving the PCs a group of allies they don't want to just leave in the lurch, then you can limit them to two kinds of travel; normal travel with their allies, or short bursts of stealthy or rapid travel that lets them use all of their PC abilities, but will still need to take them back to their allies sooner or later.
Minions are also a great way to softly nudge the campaign along a particular moral path as well. Having otherwise ruthless and loyal NPC allies balk at a suggested course of action is a great way to suggest, without judgement, that the party might want to find another option, even if looting the village, burning it, and scattering their stolen dragon-scales to start a war between the kingdom and their nearby draconic enemy would be a really great plan. It also provides a much stronger justification for ruthless PCs who want a good reason not to take the horrible, optimal path; if the long-term hobgoblin bodyguard of the wizard would be really sad if the wizard started leaning into necromancy, then the wizard would lose a friend and ally even if the party is fine with it, so the player has a built-in excuse for their PC, who has every other in-character reason to start their undead army, to hold off. And, of course, using NPCs as morality pets means that when you as GM have another villain threaten the beloved allies of the party, you're giving them permission to take all the breaks off.
And finally, to that point, minions present a great soft spot for villains to target. PCs often don't have strong or significant relationships with their families, simply because families rarely come up in play a lot, but going after the party's beloved manager, who has been canvassing taverns and work-boards from the beginning of their journey and got them their very first assignment to exterminate the dire rat in a grandmother's cellar, can produce a similar effect, and one that every PC can partake in equally. NPC allies also offer a way for the adventuring group to get in over their head without it being any PC's fault; if the PCs do have an NPC whose loyalty is unquestioned and whose service is of great value most of the time, then having them screw up and need the PCs to bail them out by going along with the adventure lets you have your hook without having to trick a PC into taking it, and makes it a better hook, because the PCs are choosing to go along with it until they can solve the problem for their ally, and not just stringing the adventure along until they can bail.
The one real downside is that NPC minions create more work for the GM. Not only do you need to juggle a bunch more sheets (even if they are abbreviated), you need to be able to drop into one of a bunch of roles on no notice, if the PCs turn to one of their entourage and ask questions you had never considered them asking. But if you do that prep work, and get in the habit of thinking through things in the world from how the core NPCs and the PCs are likely to see them, then you'll end up with a more detailed, more lived-in world.