Would the c64 have sold more with BASIC commands for graphics and sound?
It is strange that the built-in BASIC did not have any such commands.
It's not strange, it's history. What is the point of all of these what-if questions about obsolete hardware?
I think it might have gotten them a few more sales initially, then more people would figure C64-with-gfx-and-sound sufficed and not moved on to learning ASM on it, and in turn not produce the awesome music, graphics effects and games that in turn helped sales later on. I think it would end up equal or even worse.
How much more do you think it would sell? It sold a lot.
The C64 didn’t have a native 80 column mode and perhaps could have sold more if it was more usable as a terminal as well? Some Z80 machines had 80 column and could run CP/M but didn’t sell anywhere near as many units as the C64.