Was listening to a podcast that was talking about fitness - the name escapes my memory at the moment - but I remember the guy said something interesting in passing: that a 100% bodyweight fitness regimen is fantastic and would be all you need ... except it doesn't develop lower back strength. For that he said, you need weights.
He didn't elaborate anymore than that but anecdotally I related to that statement, all I do is at-home bodyweight fitness (can't afford a gym membership atm) and yet I still from time to time strain or carry lower back pain from random activities.
Feel free to add any of the dozens of lower back exercise you'll find if you google "bodyweight exercises lower back" to your regimen rather than take some guy's word for it.
Even the pushup uses lower back muscles, like any plank.
Without progressive overload the maximum strength of the muscle is very limited. Doing a bunch of pushups or planks will improve your ability to do that exercise, but you can't do pushups for a year and expect to squat 300 pounds-- the muscle growth just isn't there.
You certainly don't need weight to develop lower back strength.
I'm currently seeing a physiotherapist once a week for lower back pains, which were directly related to lack of lower back strength and flexibility. Most of the exercises I'm given to do at home (which are doable at home AND have low probability of injuring myself because of bad form) don't require any weight.
Exercises are mostly core strength ones, meaning plank and related ones.
I see a lot of advice about deadlifting and other exercises weights, and I'm wondering just how many people injure themselves. Sure, with proper form those are going to be good, but it's also easy to injure yourself because of bad form if you don't have a trainer.
He didn't elaborate anymore than that but anecdotally I related to that statement, all I do is at-home bodyweight fitness (can't afford a gym membership atm) and yet I still from time to time strain or carry lower back pain from random activities.