Pure cargo-culting. There are circumstances in which it’s perfectly appropriate to compare floating-point data for equality. There are also circumstances in which a comparison with some tolerance is more appropriate. Understand what situation you’re in, and understand the tools that you’re using.

Oh, there must be a Common Lisp predicate that addresses this. prettymuchequalsp?

More seriously, I remember APL\360 SETFUZZ from long before many of you whippersnappers were born, which told the system to disregard so-many bits in an 'equals' evaluation.

FP implementations are generally evil, and errors cascade in irritating fashion. 50% of a numerical analysis class I took once was dedicated to error estimation. Stick to rationals if you can - it'll save your hairline.

Comparing floats is sometimes useful. For example, if you are testing that you have copied a data structure correctly.