Why? What material difference does it make to anyone? At any time in any round a large percentage of players are not present at their board. If that doesn't make a difference, why should it make a difference if they are there at the start?However, on another occasion, I saw a player stood chatting on the concourse outside the building after the official start time and only went into the playing hall to start the game several minutes after the clocks had started - that is what I think should be prevented.
Of course there is arguably actually a materially relevant reason for forcing players to stay at their board DURING the game - it severely restricts the potential for cheating.
What do you mean "punishment"? Do you dispute that a player with less time has a disadvantage, 'self-imposed' or otherwise? Surely any penalty, even a draconian one like defaulting, is 'self-imposed', so i'm not sure why that is relevant? (although of course the extent that one arriving late at the board is always "self-imposed" is disputed).Yes, chess has the time-fault penalty for late arrivals, but it is the player who self-imposes that "punishment" rather than receiving it from the authorities.
You also ignore a major objection for many (similarly the mobile phone law) - the fact that they might "BENEFIT" from the default law. Most people play chess because they actually want to... play chess. When they first introduced the law at the Olympiad one guy in a minor team won THREE games by default. Pay large amount of money to play in an Olympiad, and didn't even get to play a third of the rounds!