Cultivation, in its simplest sense, was a holistic transformation and evolution of the body and soul. So even when one was crippled and lost their cultivation base, they didn't lose everything. Some fruits of their cultivation still remained—such as the transformations to their bodies—advantages that could be passed down through their bloodline.
This was why cultivating clans placed the highest value on bloodlines. A strong bloodline could sustain a clan's prosperity for generations to come. It was also why clans rarely evicted members who became crippled. As long as your bloodline was decent, you still had a purpose—you could sire more descendants to strengthen the clan. This didn't just apply to those with crippled cultivation bases, but also to those nearing the end of their lifespans with no hope of further advancement.