Answer:
They do not permit unlimited debate due to size.
Explanation:
Before a bill goes to the floor, it goes through the House Rules Committee, which passes a rule to accompany each bill.
Closed rules strongly limit or forbid amendments.
Open rules allow for anyone to propose amendments.
Whereas in the Senate, there are basically no rules. (you'd have to look up specifics for yourself but in general it's because they have a higher knowledge of legislator)