Would be awesome to see. If something comes of this please let us know. I am currently learning more these days to see what I can do to make Bitcoin work for our community.
No it's not a must default option. Not everyone uses or cares to use Bitcoin. The reason PayPal is the only one implemented in core is because for the most part it's the most used payment processer.
With the recent developments of bitcoin and its increase of popularity it would be a welcome feature to have the bitcoin function of stripe functional. Stripe is already in core.
Like this suggestion if you want bitcoin in core: https://xenforo.com/community/threads/stripe-bitcoin.131133/