In writing for strings, the double stops you typically see are thirds and sixths written for a violin solo. In a violin concerto, for example, this gives the soloist a chance to show off some harmonic color and sound fancy. On the violin, these intervals fall comfortably under the fingers of the left hand, and a proficient player can easily play them in tune, and with vibrato if appropriate.
If you have a big chord with a lot of notes, there is typically no reason to have a string section play double-stops. They're going to sound better playing divisi. The strings are supposed to be the main, sustaining part of the orchestra that is almost always playing. Double-stops are a special effect, and it's not idiomatic to have the strings playing them a lot of the time.
Some intervals are awkward to play as double stops. Fifths are awkward to play on violin, viola, and cello, because the two fingers can't be at the same position, so you have to use a single finger across both strings. For similar reasons, fourths are awkward on double bass.
In symphonic writing, the kind of standard default would be that the basses and cellos double each other an octave apart. I don't think a double bass can play an octave double stop, except maybe in the extreme high positions.
Most chord voicings use wide spacings for the lower notes. So if you look over the possibilities, probably the most reasonable double stop to give a bass player would be a fifth or a sixth. I'm not a bass player, but I believe the sixth would normally have to be played in thumb position. But there's no obvious, common reason why you wouldn't just give the top note of these intervals to the cellos.
(along with triple and occasional quadruple stops)
String players roll these rather than playing all three or four notes simultaneously. This is more the kind of thing you'd write for a soloist, and basses don't often get solos. You hear triple and quadruple stops, for example, in the Bach cello suites or in the Telemann viola concertos.