In 5e ALL swords don't break. You see the difference, right?
Sure. But most campaigns don't deal with ALL swords, do they? They deal with the swords of the protagonists and their enemies.
It's pretty clear that there are many other swords out in the fictional world (even if the DM hasn't introduced them). So, really, we're looking at the career of PCs and their exploits, and in that case, perhaps they go their entire career without having a weapon break.
Or, and here's where in an almost paradoxical way, a system that has less hard-coded rules can actually replicate this better; perhaps it's assumed that the PCs repair and/or replace their gear regularly when they go to town. In classic D&D where you track GP and other treasure and belongings, this isn't the way it's handled, but there's no reason that another game can't eschew the tracking of GP, and therefore allow such gear maintenance to be accounted for in a narrative sense.
Again, this is where "no system" is probably better than having a system. The tracking of every GP and its use actively gets in the way of the "realism" you're striving for.
Most campaigns last longer than weeks, and involve fights. Even one fight against something with hard scales, metal armor, weapons, etc. will cause nicks that need to be fixed. If your campaign only lasts a very, very, VERY short time and has no fights with anything other than oozes and other super soft things, then sure.
Again, this is all assumed to happen in the same way that other forms of maintenance happen....bandaging wounds and eating meals and all other forms of mundane activity that it's not fun to focus on. If you prefer to handle it in a more mechanical way, then you can certainly introduce such a rule.
If your happy with these rules, that's great. If the game feels more realistic to you with them included, that's also great.
Just don't tell people that your game is more realistic than theirs because you use these rules. Because that's not so great.