It also depends on how hot the housing market is at any given time. Often time a realtor is just someone who decided everything else was too much work. (My whole family has been in the business for almost 70 years, both commercial and residential.)
On the buying side, they do more such as drive prospective buyers around to look at houses, though it's been long enough since I bought a house that I don't know how much virtual tours have replaced this. Either way, it's not what I'd call difficult work.
I've bought and sold a handful of properties in a couple states through my life and have dealt with probably 2 dozen realtors in some professional capacity, and only 1 has been what I would call "good" and that was basically just him giving us insight into the market, being willing to tell us not to buy a house because it wouldn't fit our needs 5 years in the future, etc. Basically just willing to sacrifice a faster or larger commission to get us what we wanted rather than just closing a deal ASAP, which IMO should be the minimum and not the mark of a "good" realtor.