It's not random at all, it's just that the national vote doesn't factor at all (only the vote in each seat does). It has the (often overlooked, IMO) benefit of

It's not random at all, it's just that the national vote doesn't factor at all (only the vote in each seat does). It has the (often overlooked, IMO) benefit of a strong 1:1 connection between constituent and MP: even if you didn't vote for the MP, a majority of your neighbours did, and the MP is still your representative in parliament. Organising locally to boot out your MP is much, much simpler than organising nationally to shift balances of power. That has got to be a factor in keeping MPs (more) honest. In PR, you can be in the deeply problematic situation that you like candidate A and dislike candidate B from party X, but you vote for A actually ends up going to B - in effect, you can only really vote for a party, not a particular candidate. This is a significant shift of power to the parties as they generally control (or heavily influences) who runs where and how the ranking that controls "spill-over" votes will end up. Parties are often run opaquely, through back-room deals and patronage, not terribly democratically.