We're talking about mindshare, not commercial incentives. There are plenty of things sold to small groups of buyers with no significant mindshare. Mindshare does not equal commercial viability or sales numbers.
As for who would pay for a Rust compiler: probably not a whole lot of people unless that compiler has something special the offer that the normal compiler does not.
The same goes for a C compiler, there are Intel compilers that are supposed to be 'better', but as it turns out, in most cases not 'better' enough for people to pay for them. But even then, I would not be surprised if more people pay for the ICC than for Ada (but I would also not be surprised if the Ada compiler sales rack up more money than the ICC sales).
As for who would pay for a Rust compiler: probably not a whole lot of people unless that compiler has something special the offer that the normal compiler does not.
The same goes for a C compiler, there are Intel compilers that are supposed to be 'better', but as it turns out, in most cases not 'better' enough for people to pay for them. But even then, I would not be surprised if more people pay for the ICC than for Ada (but I would also not be surprised if the Ada compiler sales rack up more money than the ICC sales).