I have a iPhone 6 and still I don’t get the iOS 13/14/15 updates why is that

Hello ~ You can update to iOS 12.5.7 but no further. Click on the links below….

Update your iPhone or iPad - Apple Support

If your iPhone or iPad won't update - Apple Support

If you need a higher version of iOS you will need a newer iPhone. Click below to shop for a new device…

iPhone - Apple Official Site

If you purchase a second hand device please take a moment to read these helpful links by clicking on below to make an informed decision…

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~

The iPhone 6 lacks the hardware, RAM and CPU to run iOS 13 or later. It is simply too old.

The last and final update for the iPhone 6 was iOS 12.5.7

If you have that, your phone is done with updates. Why? It's too old.

You are probably using an First generation iPhone SE, which looks like a 5s, but is in fact newer than a 5s.

It uses the CPU and RAM from an iPhone 6s, which means it can run newer versions of iOS.

An iPhone 6 cannot run anything past iOS 12.

Because iOS 12.5.7 is the last version for an iPhone 6. That's why.

But my iPhone 5s have the 15 update

No it does not. If iOS 15 is installed, you might have an iPhone 6s.....not an iPhone 5s.

Check your Model Name.......Settings > General > About > Model Name

What is it?

No it does not. An iPhone 5S can use iOS 12.5.7, no higher.

I don’t get tho I know it has ram but iOS 13 would run on it since iPad use iOS 13 with a8 chip despite higher ram why did apple stop iPhone 6 with 5s

No one on a user-to-user site will have any kind of "inside information" regarding decisions that have been made by Apple marketing and engineering.