This topic calls to mind Tim Gunn's comment, “If you want to dress to feel as though you’ve never gotten out of bed, don’t get out of bed.”
That said, I find most of my work, weekend, and formal clothes quite comfortable even though they have a tailored look. For example, I have a lot of dresses with fabric belts (like self-belting wrap dresses) that create shape without constriction.
Also, I have different thresholds for different activities: in a meeting or at an event, I find high heels, a sharp blazer, etc. to be well worth it, whereas if I'll be at my desk writing for a few hours, I'll slip on flats and a cardigan, or if I'm at home, a comfy nightie.
It's a balance of the power of an external image, which may require slightly less comfortable clothing, vs. the value of internal concentration, which may thrive in more comfortable clothing. Or at least, that's how I feel, but some studies show that suits, labcoats, etc. actually put people in a mindset to perform better on tests, so it's hard to say whether we actually need comfort or, along the lines of Angie's original question, have simply have come to expect it.