They are not! I don`t have sign for bitcoin on my keyboard too, I don`t know for such keyboard that have crypto signs, but maybe there will be. not maybe for sure there will be such keyboards in near future. It would be interesting, I would buy such keyboard for sure, and many others too.
That is actually a great business idea, when you think about it a little.
I assigned the Bitcoin symbol to my keyboard as key combination shift "menu", like so ₿.
If you are on Linux you can read my own thread here. For other operating systems is just a matter of assigning a key to the unicode Bitcoin character U+20BF. This symbol was added in 2017 to the unicode charts, yes i know the forum can do it with [btc], but the unicode works across all unicode programs, which are nearly all these days.