Why aren't core fighters standard for mobile suits?

Because it's an additional complex system that needs to be maintained to function properly and mooks aren't worth giving ejection seats.

>>15319706
They found out that you can just make escape pods.

>>15319719
Core fighters can be used as escape pods.

>>15319765

Not as quickly or as easily produced.

Plus in the time it takes your little jet to transform you're dead. Better to just spit the cockpit out

They're obsolete once beam weapons become a thing, because beam weapon hits are either a subsystem disable (can keep fighting or run in any case except a leg hit under gravity, and even most CF designs aren't reliable under gravity) or turn you into an instant tacnuke.

It's only with old kinetic weapons like the Zaku machine gun where you'd be left in a situation where you're about to completely lose power without having already become a puff of smoke.

Remember that Arios went straight for the core fighter and ripped it out right before the kill?
Sure, it's a good feature, but it's still, if not more, open to attacks.
That said, only Ribbons' personal innovade buddies got this feature in their mobile suits.

>>15319706
Cause buiild-a-block gundams are dumb and make no fucking sense.