Ibe made a ton of progress in both size and strength since incorporating 5x5. For me... the need to evaluate my 1rm is to stay within the 75-85% of 1rm range... which, in my case, has gone up since starting. I guess you don't NEED to evaluate it but I choose to do so and I have been lifting with a few powerlifters recently who have pushed me in a different direction and it shows in my physique.
I also just like to move heavy ass weight so maybe that's all I'm trying to do really