My understanding is it's very difficult to get into Wharton MBA without having worked a bit first. Even the "out of undergrad" admits usually get in via a 2+2 program where they spend their first 2 years working at a partner company. I believe most top MBA programs are like this, and everyone I've encountered from a mid tier MBA was doing it part time while working because their company paid.
Not saying MBAs have a ton of practical experience going in, and I wouldn't be surprised if the professors are pretty far removed from any practical experience. But I also don't think it's accurate to say most MBAs haven't worked a real job before. [At least not most MBAs that the average SWE on HN would encounter. People that got an MBA from Random U because they didn't know what else to do are probably not being hired at major tech companies.]
There's a very big difference between having worked 2-3 years in industry and actually being an experienced expert in that industry. The latter usually takes a minimum of 5 years in my opinion. Also note the industry most MBA students come from is itself consulting or finance, although again that varies by school and degree type (part time programs, for example, tend to skew older and more toward general Fortune 1000 employee students).
Not saying MBAs have a ton of practical experience going in, and I wouldn't be surprised if the professors are pretty far removed from any practical experience. But I also don't think it's accurate to say most MBAs haven't worked a real job before. [At least not most MBAs that the average SWE on HN would encounter. People that got an MBA from Random U because they didn't know what else to do are probably not being hired at major tech companies.]