because we got there first. WAAAY Back now, set your wayback machine for STO's release of Klingon Content....
Deep Space Science Vessels
More Science Vessels
Bird of Prey
Carriers(at Level 40 only-the only KDF ship with "Science ship" abilities was the Vo'quv)
In the intervening time, we got a T3 Gorn sci-ship (z-store only) followed by another Zstore only sci ship, and the orion carriers (two of 'em, and they're Z store ONLY)
Right about Season 5? (I think it was 5) Cryptic gave the Feds the Atrox-their first carrier, and then the Armitage-a good Escort and good carrier blended with none of the weaknesses of either class.
Means the Federation's late to the whole "carrier ownership thing".
(Not that we're doing a lot better, mind you...most of our stuff's not changed since it was released many moons ago, and some of the KDF designs are a bit long in the tooth...)
Now...go to your shipyard, and count the number of both Carriers, AND science ships. Then, if you have a Klingon alt, go to the yard, and count the number of Carriers AND science ships.
there are threads in the PvP section that compare capabilities like-to-like, or you can write it down when you do your counting.
Why do we have better pets? because we don't have a hell of a lot else going for us, dude.
at least, in terms of ship options and choices, and what we have in those options and choices for "Vessels with sci powers" is damned limited, and usually one or two steps worse than what you, as a Fed, can get for FREE, or for LESS from the store.
Even "Fleet" level vessels.
Carriers were one of the "Differences" KDF had, and one of the reasons often used why we did not get a good selection of science ships to go with the mediocre Raptors and less durable Cruisers.
(the other being BoPs, vessels that HAVE to cloak because their hulls, shields and weapons count would embarass a Fedscort two tiers lower in the chain!)
As for the reasons behind why we have better pets still? Pets are easier to code than ships, they coded our pets first, and the new paradigm is such that "good" new-build pets are going into the "Lockbox faction" list, instead of into the general-availability store. Meanwhile Feds get Danube pets that see right through Cloak and tractor-spam faster than anyone can hit their buffs or escape-making BoPs one of the easier things for a fed carrier-equipped team to kill, along with any OTHER Klink ship that tries to close range to fire before decloaking.
"when you're out of Birds of Prey, you're out of ships."