[nimih]

In practice,

a) most situations that come up in poker just aren't that complicated -- if you're good at mental math, you can compute the exact odds for the most common situations in your head with some practice

b) there are some simplifications/heuristics you can apply if you're willing to be off by a small margin of error -- e.g. "if you have x outs, you have approximately 2x% to hit one by the river for each card remaining" is accurate enough for most players in most situations

c) this math ends up being extremely useful in practice, because "reading" someone (which is usually just logically deducing reasonable possibilities for what is in their hand) is only useful if you can then use the information to determine whether it is profitable to make/call a bet, which requires knowing your likelihood of winning.