There was so much to do (Character development wise) that if you do it right, you will have no time for alts, and will be busy leveling cooking, fishing, weapon skills, getting rep for certain factions, leveling skills. Back in Vanilla only people who had alts were the people who built Smurfs. They had no time for multiple characters, unless they didn't really work on development, just leveled to 60 and started again.
I recall having to RUN where you wanted to be for 40 levels. Then have a standard mount till level 60. At level 60 only you got the Epic mount, and then still there was no flying. Only Flight paths which you had to actually discover. I remember the Warlock quest for the Epic mount taking WEEKS to complete for a "Free" Mount.
Farming took ages to get the gold you needed to buy the Epic riding skill. 5k Gold didn't come as easy as it does now...
I made an alt right at the end of vanilla but I started later (beginning of 2006). I had made a few smurfs for level 19 WSG fun heh.
One thing I really remember is basically killing mobs for about 10 levels because questing wasn't that good, not sure if I made a mistake (probably did).
The other thing was because people didn't really have alts, you kind of made do with them as long as they were half decent.