Well its one option that competitive users might employ but generally friends playing are out there to have fun rather than win as quick as possible. Also large competitive team games (i.e 3vs3) help fight off against any such tactics for a single player.
Im suprised so many agree as you hear the way devs talk about such things and you'd think no one like those aspects of RTS's and that all users are interested in is action and fighting. To me a long period of building up bases, walls, armys and then bringing the fight to the enemy (or vice versa) means a lot more than had it just started with the fight in the first place.
I know what you mean, I played vs 4 hard ai's with a mate in AOE2 just last Thursday, good fun with building a base and taking your time

But any competitive match will be about rushing, even 3vs3 game, they will just swarm one of the three with 3 people and if you have a rubbish team which doesn't back you up or strikes back in the meantime you're dead...
Base building is bloody boring.
Each level, build a base, from scratch, over and over and over again.
That isnt how it works, it isnt how wars are fought, it isnt how anything is done.
An ideal RTS, would be one with the war mechanic of the total war series, and the ability to decide yourself when where and if you choose to build a base after expansion of your territory, or just a forward outpost, or a compound etc etc etc. and then decide as time goes on whether it turns into a town, what buildings you build and so and so forth.
That is your opinion, although I'm fine with Total war and civ style, base building is what makes RTS games so much better. I really can't stand WiC for example, it just bored me to death same old fighting over and over. I also like building a nice looking and very functional base.