TLDR : Yes. Anything that can increase your survival within a survival game is worth purchasing, within reason.
The long part here is how to use your reasoning and logic skills in a game that abandons most logic and reason to wierd , mostly unseen rules.
Armor in Tarkov is very similair to how you would see it applied in an MMO or RPG, both of which are a part of Tarkov's DNA. It isn't meant to be a complete blocker of damage, rather it is a deterrent to certain types of attacks from one hit KOing you.
If your goal is to survive your raid, armor is always worth it. It is the single buffer you can put between yourself and an attack with minimal debuffs to your character.
The great majority against armor will argue that, what's the point of an Altyn if I just get one tapped every time I wear it? Unless you're running at the loudest gun you hear every raid, you are not always getting one tapped through an Altyn, you're just dying more than you think you should.
The odds are, out of ten PVP exchanges, an Altyn CAN save you from roughly half of those on any map that isnt Interchange or Labs. And so can the Ulach and Ratnik as well. And this is just helmets, not even getting into body armor which is even more useful.
You wear the armor for the chance at survival you would not have normally had. That M61 round was going to one tap you regardless right, but what about that M80 ammo salad the the next guy is shooting? You could very well tank that and get the kill. Or the guy who cheaped out on AP 6.3 this raid? His Vector sounded scary but you tanked the first volley and you're a better shot. He probably dies there to you instead of you dying to him because you didnt at least wear a helmet.
Tarkov is all about chances but we tend to forget that when we're looking for a guarantee to our survival. There are no guarantees in Tarkov, but you can increase your odds. And at the end of the day, that's what survival is all about.