I hardly have any memory left on my laptop even though I hardly have any apps. Why?
Get the "Treesize" program and you will know.
Too many programs installed
Because the memory is full.
Nobody here can find out what you've littered the storage tank with. You have to do this on your own.
Because you have a lot of data stored, regardless of the number of programs.
It could also be that you have a virus
let a virus scanner run over there