It would be very unusual for a Traveller to have all of them - anyone running into this problem?
Yes, I run into it all the time with engineering, electronics, language, profession and science. I always need all four for electronics and engineering and have needed as many as 8 for science and language, though both of those were one offs. Still often need 4 for both.
Any competent engineer needs all 4 electronics and engineering because he will have wildly different modifiers for each depending on specialization, equipment and augments. Same with a scientist in science or a linguist diplomat and language.
So all are not needed for each character but since it's a generic sheet, best to cover all bases.
Honestly, I would prefer Athletics, electronics, and engineering, to just list all the sub-skills in those listing because they never change and noting the modifiers for each is something I always do anyway.
I've never used all the pilot slots, so either drop it to two, or go head and list all the sub-skills since there are only 3 anyway.