In gaim's case, it has its own weakness too you know
Like it's too bulky and not lighter than any of his form before, so came kiwami, which is the ulti power he could have, albeit a lill too weak than kachidoki, but yeah, this final form screams "supernatural" power is much more prestigious than anything
Type tridoron was also the same..while its predecessor's already strong as ****, it also had its issues, hence combining with krim was the ultimate choice to the problem
The way i see it was, the debut of mid upgrade were quite spectacular than the final form..like theres no greater stake for the battle so that the final resort to solving that is the final form of the rider itself..