It will be useful to limit the number of request for a specific library. Likewise for loan limits.
If an institution has more than one library then it may want, for example, to allow a patron to borrow from several of them. Then the order limit should be correspondingly larger. However, if the loan limit is larger than the request limit, this situation can be confusing for the user. For example - a patron has a request limit of 10, and loan limit 5 in Library A and 5 in Library B. However, for the moment he can request 10 books from Library A, and when he comes to the library, it turns out that he can only borrow 5.