Good managers can measure effectiveness. The problem is it's hard to quantify to higher ups, and even when you do quantify the data, it never beats the sales guy drinking with the boss and knowing the boss's taste in wo/men.
Had a lowball offer from a company once - had some friends working there. I could see from some earlier code that some really basic web knowledge was being overlooked. I won't go in to details, but... this was something I'd pointed out to one of the managers there (met at a local meetup). Fixing it then would have taken about 2-3 hours, scanning all the code to ensure it was in sync. Instead, the problem spread as they grew, and it's harder to fix when there are dozens of staff and thousands of files in use vs 5 staff and a dozen files. It became a 'this has to be fixed in order to close mega-deal X integration with company Y', and it took multiple devs several weeks of full-on effort to rectify everything.
How do you quantify that? "Please, take my advice, doing this 4 hours of work now now will save you >$50k and weeks of opportunity cost in 4 years". Generally people don't seem to care.