Swapping it doesn't really work because both people just literally swap the same amount, and nothing really changes. It can still be tracked and the swap would still presumably go to the same address, making it more obvious that the person still has "x" amount of Bitcoin, just with a different string. Mixers can send smaller amount over a period of time to a different address while also mixing up the strings and making it harder to follow, and it can make your address look like a completely different one.

Hypothetically swapping would work, but it's harder to do that than it sounds.

Why do people use mixers?

Will you accept Bitcoin from just some random person? This could be some money launderer or someone who just murdered someone for payment or some paedophile network hiding their tracks. I

know I will not do that, so for that reason I send all received coins through a mixer services, just to rinse them a bit and making sure I am not pulled into something I did not do. I would much rather

mix my coins than sending it to some unknown person, with shady intentions. 

Yeah, plus more if you are exchanging with people who turned out to be deceptive. You may be losing the 10 BTC. bitcoin exchange with fiat I think the same, but you should choose a trusted website.

No. Instead of trusting a faceless organization, you would now be trusting a single individual who would get firsthand knowledge of your Bitcoin address. If you know that individually personally, then the track will be ever so closer to you. Otherwise, you just trusted someone who doesn't owe a shred of loyalty to you with information that would lead back to you.

If you want to thoroughly mix your coins, then repeatedly swap them for altcoins (with not-so-volatile values) under multiple accounts and using different IP addresses, transferring them across multiple wallets during the process. That will require a lot of effort, and your balance will take a hit from multiple fees incurred, but you'll obfuscate your tracks to a degree that it would become obnoxious to follow it. You can even throw some into a mixer along the way since that's what they're for. Whether mixing coins itself is justifiable, I leave to your own rationalizations and delusions.

Congratulations!!! You invented the coinjoin https://en.wikipedia.org/wiki/CoinJoin

I dont see the point in it

You can check out the nice inforgraphic that bitmixer has on their website:

https://bitmixer.io/how.html

It clearly shows why you use a mixer instead of just straight swapping coins.

You dont make profit with mixing either.Mixing is done to keep coins untraceable.
Swapping is risky as you act on the trust of other party.Mixer usually use mult-addresses to mix coins making it harder to trace.Bitcoin swapping,on the other hand,is exchange of coins between two addresses that doesn't makes it untraceable

swapping bitcoin just like the method you're explained above is such wasting time and effort,and keep in mind that you can't trust anyone in bitcoin world so it's definitely not more useful than mixing while you could've done it with ease