Yes, people here are already cyclists, and have long forgotten what it's like to start. Also, many started when they were younger, lighter and fitter. That doesn't translate to what most new riders experience, which can be a very tough 5 miles, after which they're pretty much crapped out.

If someone can't run more than 1/2 block or so to catch a bus, they're going to suffer on their first few rides. However once they get past the initial "break in" phase, then improvement can happen pretty fast, and most healthy people can get to where they can ride 50 miles in under 5 hours within half a season or so (if they work at it).

When helping folks get faster or stronger (longer) I usually advise mixing hard, fast shorter rides with slower buy long rides in some sort of alternating pattern. I also try to find short steep hills, and long grades and mix in some riding of both. The key is to focus on your weakest issue, and work on it, mixing in general training of other rides.

In any case, even if your first time out you couldn't ride a mile, that's still one more mile than before.