There's more to deciding whether to create any particular index than just whether it makes any of your queries faster. Each index can speed up SELECTs, but it also slows down any write queries on those tables. Each index also takes up space on disk and memory.
Then there's the question of how often which queries are run, and how important their performance is. Maybe query X is run by some background process, so nobody will notice if it takes 10x longer, but indexing the table to speed it up will slow down the INSERT statements on that table, which are in the user's path and will be noticed. Maybe it would also tax limited disk space on the DB server and require a hardware upgrade or a complex multi-server setup to work.
Coming up with an optimal indexing scheme for any particular database is a series of complex trade-offs which include taking customer needs and business requirements into account. I don't think it will be practical to do it automatically anytime soon.
Then there's the question of how often which queries are run, and how important their performance is. Maybe query X is run by some background process, so nobody will notice if it takes 10x longer, but indexing the table to speed it up will slow down the INSERT statements on that table, which are in the user's path and will be noticed. Maybe it would also tax limited disk space on the DB server and require a hardware upgrade or a complex multi-server setup to work.
Coming up with an optimal indexing scheme for any particular database is a series of complex trade-offs which include taking customer needs and business requirements into account. I don't think it will be practical to do it automatically anytime soon.