[iksmudge]

OK, I'm probably being picky/thick.
Why is there a trend for front Tyres to be thicker than back one's.
Will somebody please explain.

 

[sittingduck]

Part of it is clearance. It's easier to put a fat tire on the front, than it is to put one on the back. Chainstay clearance and brake clearance can be an issue.

 

[mattt]

Assuming that you meant wider...

A wider footprint up front provides more traction where its more necessary: It is much easier to recover from loss of rear wheel traction than loss of front wheel traction.

Also, a larger volume tire can act as a bit of suspension when needed.

 

[sealclubber]

yup. when you see someone do a drop-to-flat like a stair set, they put their rear wheel down first, then use the bike as a lever to pull against the front so it sets down a bit softer, a bigger front tire helps soften that blow