Why? lol

This simply reflects that bitcoin is still in its infancy.  There will be many more options for converting bitcoin to fiat and vice versa once people get comfortable with what bitcoin is and how it works (i.e. including regulators).  There is no getting around the fact that you want to swap BTC for fiat - that's where the bottleneck happens.

That said, $50K is not a problem.  There are plenty of traders on localbitcoins.com who can deal with large amounts (though admittedly that requires you to go out and sell your coins).