As there are some items that require flooring in place before you can build them, I find it odd that you can then delete the flooring out from under them.  Intentional, or just weird?

Yep that's a know bug and will be fixed in Version 5 on Monday

I don't want to create new topic but I would like to ask.

 Why only few items need floors and others don't (and can't be built on floors)?

It shouldn't be like some items have to be placed on floors and other may be placed on floors?

Thanks Denki!  I'm curious about the reasoning behind floors as well.  I like having to build one to put down equipment, but it would be nice to be able to put storage next to them without interrupting the floor to do it.  Not a big worry, but since we are on the topic :)