The reason the clock needs to stop on first downs is they are completely inept at getting the chains and ball set. Specifically near the end of the game this is important. If a team is trying to tie/win a game, but loses on time because they can't start the plays fast enough because we are waiting for the fat old officials get ready that is worse than the games being longer. Games need to move faster, but the issue isn't really the pace of actual play. The issue is long reviews and ridiculous time outs.
The length of these reviews is the issue, it's ridiculous. What I really hate is like yesterday, after a play is over they go to a commercial TV break, which lasts what seems like forever, then when they come back after the commercial break the official says they are going to review the previous play. Wut? Why weren't you reviewing it the last 5 mins during the commercial break?
And some of these reviews are really obvious plays which shouldn't need reviews in the first place, but even so, it should take like 20 secs to look at and see the obvious correct call, but yet it still takes them forever.
And how about having 2 or 3 spots on the sidelines where the official can go to talk to the booth? Sometimes the official has to jog or walk almost the entire length of the field to get to the mic where he can talk to the booth, then makes his ruling, then has to jog or walk all the way back down to where the line of scrimmage is.