Wasting addresses is a good security measure.  A lot of cryptosystems attacks involve comparing multiple outputs from the same key and calculating portions of the key from properties in the repeated outputs.  Historically, I think Enigma was first broken this way.

Generating a new address each and every time reduces the chances of an attack like that being possible, assuming that weaknesses of that sort are someday found in SHA256 and RIPE-MD160.

Oh, and if we assume 100,000,000,000 people in the world, and each of them doing 10,000 transactions each day, it will take 3.8*10^30 years to run out of addresses.  The first address collision will, of course, come a bit sooner than that.  For comparison, the current age of the universe is generally thought to be around 1.3*10^10 years.