> net positive profit-wise over time.

There are definitely many customers you should drop, but business are not even that interested in retaining profitable customers. The problem is with the "over time".

Management are rewarded with bonuses and options that focus on the next few years so they are not really interested in how profitable a customer will be over the next ten years, only over the next one or two. Small businesses and family owned businesses are different, but for a big, widely held, professionally managed business the incentives are all short term.