Can frequent light bicycle commuting severely damage pants?
Absolutely. The thicker your thighs, the more friction, and the quicker the pants loose their thread. This happens relatively irrespective of material, even jeans can wear through rather quickly. I guess that specialized bike wear uses materials that are much less prone to this, but I have not tested that myself.

Of course, saddles with sharp edges do contribute to the wear. Yet, one pair of pants in a year is not too bad. I've worn down jeans within two or three months, simply by biking a lot more with them than you do.