I need some second opinion related to, yes, RELATIONSHIPS

My application containing approx. 90 local tables and 60 common tables (shared tables)

I have not set up any relationships on the common database nor in the local tables in my application. All relations I'm using is set up in query and SQL (as described to be the most common way to set up relations)

As most of my query consist of combinations local and common tables I assumed it makes no sense to establish relations at common table database.
Am I right ?

Finally, will I gain any benefit at all to establish relationships in my application?