Why do they say you'll be wheelchair bound in your 50-60s?

I see many guys on Reddit and Looksmax say that LL is not worth it because you'll be paralyzed in your 50-60s.

Now, I know that it's not the case if everything goes well but where did they get the idea that all people who undergo LL will have mobility issues in their later years of life?

Sampling bias and the vocal minority. Negative cases are magnified and are brought more attention on the internet which gives the impression that wheelchair bound cases are the norm when in fact, the opposite is true with qualified surgeons.