Why do spiders spin a web?..

I have way too much time on my hands sometimes !  ... just for fun.

 
Why do spiders build a web
Without a tiled roof?

No shelter there without a care
Less than waterproof

In wind and rain he hangs on tight
A task he so enjoys

Never seems to have a care
worries not of noise

No doors to open glass to clean
And always fresh and gleaming

could it be he builds a web
to cut out all the cleaning?

I doubt it is the simple truth
our spider seems so busy

Round and round he spins his silk
So rarely getting dizzy

Well maybe he just likes fresh air
And dangling from his castle

Or maybe building tiled roofs
Is just a load of hassle.

What thought has he of human needs
Or why he needs to shelter

He spins his web and stands well back
And says "wow that's a belter!"