While I learned about the modulus operator at a young age, I grew up programming in environments where "nobody" used floats because the CPU's in question didn't have FPUs, and floating point operations resulted in costly library calls.

While only "older" (I'm 39) developers will be likely to have been in that situation, it took another decade after I moved onto hardware with FPU's before I worked on anything where we actually used floating point math.

Instead we'd be working with fixed point stored in integer. E.g. for financial systems, floating point is a nightmare. Working with fixed point to whatever number of decimal points our accounting department wanted (5-6 typically) for tax calculations and the like was preferred.

So there are large number of areas where people can have worked successfully for many years without ever using floating point.