Wondering if it's just my problem, or do a lot of people also feel that their glasses could have been a lot more comfortable?
Weight: some glasses are very heavy and the pressures the pads make on the nose are too high for comfort.
Pad angle: The nose pads should sit flatly on the skin of the nose. If the pads are angled relative to the skin, the edge of the pad digs into the skin.
Skin moisture: sweaty skin leads to overgrowth of bacteria under the nose pads.
Earwing curvature: Where the ear wing curves around the ear must be measured properly, both to avoid putting undue pressure on the ear cartilage (too tight) and the keep the glasses from moving around too much (too loose).
Earwing Twist: For want of a better term. Everybody's ears are slightly different in the position on the head. That means that your earwings might need to be angled away from the eyes differently. (If you put the spectacles, opened up, on a flat surface like a table, does one earwing hang above the surface instead of both earwings resting on the table.)
Bifocal Vertical position: If the bifocal transition is not at the correct level, you may find yourself holding your head at an angle which is not particularly comfortable.
You'll most likely find that your optometrist can make the most difference to your comfort. A good optometrist will spend quite a bit of time getting all the options correct.
Once again, for what it's worth, I find that women are more likely to spend the extra time to get the job done properly than men will.