Will the crumbs/dust cause damage?

Simple question i have here..

I'm a type of guy that as long as the machine works, i dont work about it having scratches, dust, whatever. (As counter intuitive as this may sound)

Well i know that there must be quite some dust behind the keyboard and just by looking i can see some crumbs, pieces of cheeze its below albeit in for some reason i dont seem some crumbs that used to be there before.

My question being...Does this dust and crumbs get into the main operating mechanics of the computer? or is it just a problem with the keyboard mounting?

So far my computer works as good as new (mid 2012 macbook pro), and looks new aside from the crumbs and dust that is clearly down there.

There is some dust on the usb ports and others though, how much can some dust on the keyboard or these ports, cause?