For some it may be laziness that stops them applying maths at the table. I suspect for many it is just too difficult.
I have an A in A-level maths and a science degree but I am flat out awful at maths. I'm literally bad at counting and my working memory is so poor I can't hold more than one number in my head at once. Serious mental arithmetic is pretty much impossible for me without learning things by rote (like times tables).
I don't know why I'm bad at it but I suspect it is just the way I am. To suggest I'm lazy would be akin to me telling anyone under 6 foot tall that they're lazy for being short
Nevertheless I do benefit from slowly doing the maths away from the table and memorizing the results or at least the implication of the results. Without doing combinatorial analysis it isn't intuitively obvious to me that, for example, in certain spots some players' ranges are value heavy or contain mostly air or lots of draws. Working through it in slow times give me insights I can use at the table while playing by feel: it gives me a better feel basically.
I've read a lot of Ed Miller's books and one of his pieces of advice is to look for how and where loose players try to get rid of their bad hands. Loose players have a choice with their bad hands; fold them, call them or bluff bet/raise. Experience will enable you to quickly identify a folder, station or bluffer but combinatorial analysis seriously improves your ability to predict when they are going to over-fold, call too much or bluff too much.
Then it is easier to spot the rare times you can bluff a station, can fold to a bluffer or should thin value bet a folder.