because it's the perfect type of plastic to use, cheap ( practically free) and they'll last for many years.
http://www.bedbathandbeyond.com/product.asp?SKU=10690463 $7, if you need it smaller then just cut it down with a hacksaw or pipe cutter. Safe, easy, cheap. Why bother with anything like these plastic spice bottles?
The rest of you, shell out the duckets.