I'm not saying it's not...
I'm saying that it's an unneeded level of detail. I would never tell a player that their character can't pick up the grenade because they didn't state they were paying extra for the cargo pants when they purchased clothing...
Same reason ammunition you buy for the Colt Government 2066 can be put into the Ruger Super Warhawk. Ease of play.
+1.
The player is of course free to describe these things, but no need to check the character sheet for "Velcro Pocket Straps" so the character can use the gear they paid for.
The problem is that it becomes very important in certain situations. A Chameleon Suit is basically an armored bodysuit, so pulling things from under the suit is problematic, to say the least. Same with HAZMAT gear or full body armor, to say nothing of corpsec or milspec hardened armor. And you'd definitely have to get high society clothes tailored to leave access. It is one of those things that can be a visual identifier, if the alterations weren't done well, perhaps spoiling a run because some manager noticed your clothes weren't quite right. It is the same reason why wearing an Ares brand suit inside an Aztechnology facility is going to mark you as an outsider to any white collar type. It is the fashion equivalent of Chekhov going up to people in San Francisco in Star Trek IV and asking them "vhere are the nuclear wessles?" in his Russian accent. Almost literally, considering the insular and tribalistic nature of megacorporate culture in the Sixth World.
Of course, this also can work for the players, as NPCs who wanted to use their smuggling compartments or other hidden gear would need to have their gear tailored to fit. That can be a limiting factor on engagements, and could give you visual clues about what kind of options those big, beefy bodyguards might have access to, and so on. And yes, one might be able to tell which corp someone works for by what kind of suit they wear, unless they are Mr. J trying to throw you off.
Not saying it would be an onerous cost, but perhaps a couple hundred nuyen and a slot of capacity to add the 'Gear Access' feature to the clothing or armor in question. Gear Access, after all, is meant to make things easier to pull from inside the armor.