Do you mean why is it so hard not to overeat carbs specifically, or just overeating in general?

Comfort food... is your low carb menu interesting enough to compete with off-plan foods for your attention? I find making low carb food too interesting can have me eating more, which isn't always what I want. But then if I'm off plan for a holiday, these foods can help get me back on plan, or intentionally overdoing heavy cream, pork rinds, liverwurst etc. can keep me from going off plan in the first place. It sort of depends on the situation, if peanuts keep me from eating pie, that's good, but when those temptations aren't around, the peanuts make my diet a little worse. Sometimes you might just need a little comfort or holiday food, and if it's more in the order of a slight diversion instead of something that will throw you off-track for a week or two, that may be the way to go.