@Neha-Rawat Exclusive means that only they, and none others, are allowed to use the illustrations during the time established π You cannot sell it to other companies or even make your own products. You've basically relinquished all your rights for the duration of the license. A non-exclusive license means you can sell it as many times as you like to other companies at the same time.
So yes most publishers would prefer it if they can, but this exclusivity prevents the artist from making money off their work which means an exclusive license should be a LOT more expensive. Most of the time the publisher can't afford exclusive rights. Sometimes they buy a non-exclusive license, but include some non-competition clauses in the contract. For instance, a clause saying the artist can't use the illustrations for a picture book while their own license is active (so the book doesn't compete with theirs) or a clause that says the artist cannot resell the rights in the same country. Not all usage of the illustrations will actually interfere with the publisher's project. For instance, what does a Canadian publisher care if in 10 years I re-sell a book illustration in Germany for the packaging of a local product?