Facebook made exactly the same mistake and I believe it is hurting their platform a lot even though they've opened new doors to support new ideas for their evol

Facebook made exactly the same mistake and I believe it is hurting their platform a lot even though they've opened new doors to support new ideas for their evolved API. I launched an app back in May 2007 right after their platform launch. After the four years the app is quite broken now and every now and then a user sends me a message about it. Today I decided to spend a day to translate all those "old" API calls into "new & improvides" API calls but due to lack of documentation, unavailability of search results due to all that legacy documentation better SEO'ed and the hectic task of re-testing all the workflows I've previously tested thoroughly, I gave up! Why should I put in so much effort in re-writing my code just because you don't like a function name or you think same functionality could be achieved by another one so this should be dropped?