I have been a professional software developer full-time for 12 years and I have only worked on one system that needed an exact decimal representation for money.

I have been a professional software developer full-time for 12 years and I have only worked on one system that needed an exact decimal representation for money. I just don't deal directly with payments, billing, or account balances. I do sometimes have to represent money, but in simulation or estimation scenarios where nobody gets cheated or audited if it's $0.01 off. Arbitrary-precision rationals would get extremely hairy extremely quickly and simply break down for a huge number of use cases. People use exponentiation, square roots, and compound interest! If a "senior developer" who actually works with real account balances doesn't understand floating point, why would you expect them to understand why they can take the square root of 4, but the square root of 2 crashes their application? Or why representing the total interest on a 30-year loan at 3.5% takes over 400 bits? The reality is that software engineers need to understand how computers work for the field they're working in. Many (if not most) programmers will never encounter a situation where they're responsible for tracking real account balances. The ones that do simply need to know how to do their job.