Oh, they use them. The problem is that each philosopher has a different precise definition that they feel is natural and matches what we "really mean" when we ask deep questions. Since most arguments and conclusions are phrased fuzzily, you end up with the following situation:

Fuzzy premise -> precise logic -> fuzzy conclusion

where each of those arrows leaves so much room for interpretation that you can build literally an entire subfield by arguing back and forth about what the most reasonable mapping from fuzzy to precise and back again might be, even if everyone agrees that the manipulations in between are rigorously correct.