I think that the shortest path problem is probably the problem that is solved most often. But if we move to problems where we need more complicated solvers, like Gurobi, Cplex, and Baron? What are the problems which are solved most often in industry (or people deploy the solution)?
By problems I mean something like vehicle-routing-problems, scheduling problems, etc. It would also be great to know why these types of problems are solved most often (easy to implement, easy to deploy, most money involved, ...).