People who want to see less teams feel that way for two reasons. They never think about the other side of it, including what it's like to lose a team.
The two reasons are (1) giving teams a better likelihood of winning a Cup within a fans lifetime and (2) concentrating talent on fewer teams would lead to a better product. Reason 1 is logical.
Reason 2, I have a lot harder time agreeing with. Yes, you concentrate the offensive talent, but you're also concentrating the defensive talent and goaltending. More high quality defenders on each team means better ability to execute stifling defensive systems. It's more likely we'd just see the same ebbs and flows to the game that we see today.