SPARQL requires buy-in into the world of the semantic web even when all you want to do is store and query graph data.

Also, property graphs wouldn't have managed to get the traction they have if SPARQL would have been sufficient. SPARQL simply suffers from being designed in a way that does not sufficiently address the needs of application developers, in expressivity, ease of use, let alone allowing easy migration of existing relational data by sharing the same type system with SQL.