Because the quantity isn't just less than 100%, it's a small minority. Chrome and Firefox are among the most widely-used pieces of software in the world. I'm not saying they don't have weird bugs, but they don't crash daily for most users.

While the OP may not be doing anything "wrong", he is almost definitely doing something unusual, or has deeper issues like malware or malfunctioning hardware.

If the ratio were inverted and most users were experiencing daily crashes from normal use, I would consider myself lucky. That's just not been my experience with Chrome/Firefox.

I would suspect a majority of the world does not keep dozens of tabs open, on an computer that never shuts down. You have to remember which forum you're on here. Any software issue, usually rears its head relatively quickly from one of our machines around here.

That's the use case I'm most familiar with. I've done this on many different machines for many years and not had anything like a crash once a day. I stand by my belief that your negative experiences are likely caused by a rare collision of variables and not representative of the typical experience among similar use cases. As I said in my post, it's totally legitimate that such an atypical experience may be caused by real bugs, but it's still an unfair generalization to say that Chrome and Firefox crash daily.

Bugs which only affect a small minority of users don't exist, nor do unusual but perfectly legitimate usage patterns?

You probably want to re-read my post, as I said neither of these things.

You're right. I was confused because in your other comment you just said they were doing something wrong, and I didn't realize you'd reversed course on that.