If your/you're & there,their,& they're sound the same when we talk then..
....why does it matter if we spell them out when writing?
I mean think about it, when someone is speaking to you, although they all sound the same, just given the context of what the person is saying, you can easily and rather automatically decipher what they are saying, so why do we even need to spell them differently?
For example:
If someone writes "there going to the movies" rather than the correct "They're going to the movies" I instantly hear "they are", just as i would if they spoke it to me.
When you speak it there is no difference in how it's pronounced, so when I read it, there is also no difference in how it's pronounced in my head. So why even do it?