I suppose another problem, is if both players are slow. Lets say one player has 10 seconds left, and the other has 20 seconds left, and they are tied 3-3 on a race to 5. They would both definitely run out of time if the match is allowed to finish. But only one will lose because of the time violation. That just seems a bit unfair to me, if both are dog slow. I don't know the solution to this.
Nothing unfair. Matches do not have to finish by score. Why assume that? He who runs out of time, gets a match DQ. Or the winner is awarded a winning score automatically.
If one is a slow poke, and so is the other. If one of them has a brain, they will play slightly faster to conserve a balance of time greater than their opponent. The other guy will then run out of time and lose before the match is concluded by score if they try to continue draining the clock.
Whomever is lower on time, it is automatically against their best interest to continue to stall and drain the clock as it significantly works against them and only gets worse. The instant they are lower on time, continuation of that strategy is going to result in a guaranteed loss if they both go down that road.
The scenario above won't happen, since players are not going to want to voluntarily engage in a game of time-clock chicken. They're not going to drain the clock down to where it becomes a contest of who can end their inning by any means possible to then slap the clock. Long before that happens, one of them is going to game it and take advantage on the table and the time management.
This is how clocks force a productive pace.
The idea here isn't to generate speed pool, or pressure the players or the game into something unreasonable. But to weed out the unsportsmanlike deliberate slow-players.
Clocks could be set with a generous amount of time to complete even a hill-hill match with safety play. An amount of time that would work for the vast majority of players and be very fair to them, and also stay true to the nature of the game. That is, not putting any undue artificial pressure on the game play which results in rushed shots and hastened decision making.
Times, race length and formats can all be set to be completely reasonable for players, and give them ample time to play their best and complete a match with plenty of time leftover and never feeling rushed.
Again, the goal is to squeeze out the intentional and deliberate slow-play tactics.
Just the fact that they are put into use will be enough to control total match times. It also has a deterrent factor. There will still be some slower players, but that's ok. I don't think that even slower-than-average players ruin the game or bring harm at all. It's the stallers that do. The snails that destroy the game will have to give up this tactic or become extinct.
The clock is a great tool, because it punishes the slow player in the event that a match time has been exceeded. There was no way to discriminate before the chess clock. Who was to blame? Who decides who was slower? Who was tracking it? No one knows with certainty. The clock makes it certain.
Shot clock is inferior pool. Chess clock preserves great play, and controls match times and is low maintenance (ie, no tourney staff has to babysit timers).