I could argue that the longer I spend taking my turn, the more time I have to think and the more likely I am to make the optimal choice. Therefore I will always take the maximum amount of time that the rules allow. When do you draw the line and call it abuse if it's well within the rules and I'm simply exercising my right to taking my time?
This hypothetical sounds silly, but it is rationally sound and I use it as an example to point out that the rules themselves are silly. Rules are very important in games. If there is no rule limiting the time to a reasonable amount, then it is simply flawed. The tabletop version has no time limit, sure. They are assuming that you aren't going to play against people who troll you. On the internet, you will inevitably be faced with trolls, so you have to control them with explicit rules. This seems so obvious to me from a design perspective.