Why is document upload size is 50MB max?

[silincone]

As I have mentioned, why is the upload size so less when telegram allows 2GB + 2GB* ?
Or, am I just wrong with my conclusion? If I am then, can you please let me know the way to do it?
And, I have very little knowledge about programming, I couldn't understand the sample echo program, so that's where I stand, I hope you understand me and I hope that you could help me out.
Thank you for your time.