I've played and ran games with a lich on the random encounter table. Explain to me why that could never make sense? There's never a chance for the lich to come home while the pcs are looting his lair?
You know what, nevermind. My ignore list, that's going on 16 years just got it's 2nd entry.
On the off chance that there's anyone out there who is interested in my line of thinking: maybe I didn't do my homework and didn't look at the table ahead of time, maybe the party is only second level and is vastly underpowered to handle a fight with a lich, maybe liches don't make sense in this location, maybe liches don't exist in this campaign, maybe there's one lich in the story and he's the BBEG, maybe they just fought five liches in the other room.
Or maybe, as is usually the case with a list, I choose something off the list that makes sense to the story, but instead of starting at one and and reading through every item, I roll and start looking near where I rolled and pick the first thing I like.