That's my secret really, the players never see my random encounter tables. They roll the dice but they don't see the table.

They include a lot of stuff relevant to what's going on more than "random spiders"

A good example is when they were trying to locate an old run down keep that a local band of bandits were using as a hideout. The random encounter table included such things as: group of bandits on their way back after a raid (successful, not, injured, not, etc), group of recent hostages on their way to freedom (escaped, released, escorted, etc), a caravan being raided nearby by the bandits in question (or others), rival bandits on the same mission, etc. A couple entries are (of course) night passes peacefully and usually there's 1 or 2 creature encounters (that can usually be avoided), and hell even a "sounds in the distance (insert kind of sound based on perception check(this may lead back to the earlier table))". And even some stuff that may lead to new adventures.

It's more work than just "creatures roll initiative" but IMO is way more rewarding, and my players seem to enjoy it a lot.

Random encounter tables is a vague term but unfortunately I think may be the correct one in this case.