Because you have just taken a third of your fleet in squadrons that can't kill ships, (plus more points on carrier versions of ships/squadron upgrade cards) and will get rolled by the first fleet you meet that is low/no squadrons, which has around 100 more points of its list devoted to killing ships than you do.
(This is all in a world now where even smalls with previously useless evades can resist your squadrons.)
So now you just need to come up with a strategy that deals with that flaw! Preferably, for your wallet's sake, before you buy the 4 squadron packs. 😄