Why?
Everybody thinks we need to sign more and more and more players until we find the right XI. It doesn't work like that and if you're not careful you end up like Chelsea were with far too many players making it impossible to put an established team capable of challenging together, while ending up with an onesie, unsettled squad full of highly rated pros that can't get a game.
We're already some way along that road with a host of players out on loan while we having a side that's already challenging but (notwithstanding injuries), with players like Ake, Bobb, Stones, Ait Nouri, Marmoush, Rodri, Khusanov, Trafford, Kovacic and a hoist of others that aren't getting any game time which will mean they become unsettled and want to move on, then we have to find replacements and go through the process of having to fit them in and get them up to speed.
That's why Pep likes a smaller squad, it's easier to give most of them enough game time to keep them happy. Too many and you get players that never get in the side and end up moving on. That's what happens with a lot of the academy players, whey several on the fringe of the team who, with all those senior pros on the sideline will the most part never get a chance. We will need a lot of them if we're going to play 60+ games a season but we can't just keep adding to the squad.