Those examples are different because they are core to each of those companies' business model by being directly tied into their revenue stream. Simply put, it makes them competitive. Therefore, those apps you mentioned have to be good if not better than what their competitor uses.

The problem is more about internal applications that have nothing to do with the identity of the company itself. Personnel management, time tracking, accounting, and payroll apps suffer from poor quality if built in-house because they are part of the cost of doing business independent of what that business may be.