Bassplayers tend to use the word "chord" in a different sense than its customary usage in the guitar world. A chord is just an interaction between three or more distinct notes, which may be reflected simultaneously, or in sequence. So, yes, one way of playing a chord is playing the notes in succession. For example, you could play a "C", "E" and "G" in succesion over a guitar's simultaneous playing of those notes, both of which would be a C major chord. Typically, though when people use the term "chord" they are referring to playing notes simultaneously. It is less common to do the latter on bass, but I really love playing simultaneous chords on bass.
Technically speaking, bassists are prone to playing chords arpeggiated, which is when they're broken up into a note sequence. It's a chord subtype (or scale subtype, depending on how you want to look at it). One doesn't usually refer to a chord as 'simultaneous;' simultaneity is assumed unless a distinguishing term like broken or arpeggiated is used.
If we want to be completely accurate, C E and G together are a C Major triad; there are a bunch of other C Major chords that are not triads, so the distinction is necessary.
Why can't you play chords like on a guitar? It would be more difficult, given the heavier strings, but I don't see any reason you couldn't make chords the same way as you could on the lower four strings on a guitar. I could be wrong, though, I have limited experience playing a bass.
It's for the same reason you don't play full chords through distortion. A bass guitar is right at the bottom of the frequency range (an upright with a C extension actually gets within spitting distance of the lower limit of the human ear). At those very low frequencies, the notes are very sensitive to the minor frequency oscillations that don't matter as much for higher-pitched notes. A bassist can play something similar to power chords and have it come out okay, for largely the same reason too. Distortion causes random frequency variations that cause a normal triad to become all dischordant and ugly.
The fifth is a great interval because of the harmonic interactions that mean it basically sounds good no matter what. There's a reason they call it perfect.
Somebody mentioned a dyad, which is really a harmonic interval. Dyads will commonly resolve better than triads or other more complex chords because there's less going on in terms of frequency interaction. The perfect fifth is possibly the most famous dyad ever, but calling it a power chord is a bit of a misnomer because it really isn't a chord at all (this is why when they're tabbed out power chords are always written with a 5, ie C5 or F#5).
Or! Have the bass player play the 3 note in the chord while the guitarist plays a power chord.
I... uh.. suppose you
could do that. I was going to get into reasons why this might not be a good idea, but frankly from an artistic standpoint I see no reason why it shouldn't be used. Try it and see what happens.
Man, we're bordering on some pretty wackyfun stuff here. Am I nerd for loving music theory so damn much?
