@RegGuyI had to get off a bus once for the same reason. Apparently, a big part of the problem is that softeners use plastic micro-capsules filled with synthetic fragrance, which are attached to the fabric with a waxy substance. The capsules are designed to break with friction. New capsules break every time the person moves, causing more fragrance to be released continually. As a result, the smell doesn't simply dissipate with time as it would if it were a normal fragranced substance.
L