I think most mathematicians are more likely to be Platonists than formalists. Formalism is also a real position in philosophy of math, but a minority one for I think two reasons. One is that the math we've developed seems significant enough and effective enough to deserve more explanation than just "it's one of many possible formal systems". Second, if you take a straightforward formalist approach, then there aren't really any interesting questions in philosophy of math, so people who think that are less likely to become philosophers of math.