It adds more math to a math heavy system (bad, but not too bad with a good electronic character sheet)
I keep hearing about how Traveller has lots of math. What math problems are you using it for?
Assuming you are being serious...
It isn't that the math is difficult but that there is a lot of it, which slows things down. A lot at times. And compared to our homebrew which is opposed rolls of a single die on each side (using different sized die) with the larger number winning, most things are math heavy.
And much of the modifications can't be pre-calculated, unless you have a huge table in your electronic character (spread)sheet.
To make a combat roll, off the top of my head you have
add/minus for skill or lack thereof
add/minus for attribute or lack thereof
add/minus for range
add/minus for conditions (may be multiple)
add for aiming
minus for having dodged earlier (may be multiple)
minus for cover (or for concealment)
minus for parry in melee
add/minus for leadership