There is a time I would have agreed with you, but the more I've played and the better I've gotten my opinion of scouts has increased dramatically. 3 scouts on pangaea is very good advice, but obviously you need to use them well.
The thing is, you are usually done with pottery (assuming you researched that first) right around the time you're done with the 2nd scout. So if there's a pantheon you want to compete for, you need to start a shrine ASAP. Or if there's not a pantheon you really want, build a granary to help with settler production and future trade route.
I just feel there are better things to build at that time of the game other than a third consecutive scout. Unless you're talking about delaying the 3rd scout until another time.
My scouts are adequate at exploring usually just having two. The only reason I might want to build another one is for side projects, like settler escorting, blocking, worker stealing, etc.
But hey, to each his/her own.