It doesn't always affect performance. A lot of business apps are mostly doing CRUD under fairly light load. It may be that beefing up the database server is much cheaper than interacting with the database in a way that, while being more performant, is also more laborious.
That said. . . yeah, I've also had my share of cases where the app ended up seeing higher load than anyone anticipated, and it's hard to even see the source of the performance problem, because, with an ORM, it takes a little bit (or, with the worse ones, a lot) more work to find out what the actual queries being executed are so that you can ask the DBMS to `EXPLAIN` its query plans.
Except, I don't find using SQL more laborious, and it if is then I'd suggest that's a problem with whatever language makes using SQL directly laborious.
That said. . . yeah, I've also had my share of cases where the app ended up seeing higher load than anyone anticipated, and it's hard to even see the source of the performance problem, because, with an ORM, it takes a little bit (or, with the worse ones, a lot) more work to find out what the actual queries being executed are so that you can ask the DBMS to `EXPLAIN` its query plans.