Well there's actually a really interesting reason for this.

So when you hear other people's voices, you're hearing it through something called air conduction.

So the sound waves are coming through the air down your ear canal, get amplified by some small bones and then end up here in the fluid filled cochlea where there's a ton of little hairs that send nerve signals to your brain which you interpret a sound.

But the difference is when you hear your own voice, you're also hearing it through something called bone conduction.

So your vocal cords and your bones literally vibrate including your skull where your ear is.

And as a result because bones tend to transfer lower frequencies, people tend to hear their own voice is slightly lower than other people hear it.

Now, the problem arises when you hear your voice played back to you.

There's no longer any bone conduction, It's just air conduction and as a result it sounds slightly different to you, which makes it feel really weird and most of the time very cringe.