Blue it is done quite a lot, now it depends on how one defines pleasure.
I just extended a trip for a couple of days on the Company. By working in a Sunday departure I saved the company a lot, they were more than happy to pick up the 290 euros for 2 nights hotel to save the almost 2K euros in airfare. They even threw a per Diem for food which more than covered Food & Beverages.
Pre roommate I used to work a lot of Trade Shows & Conferences. There was a lot of pleasure to be found in these outings, sometimes multiples in a day. BTW the food at these events was always quite good.
Interns and University new hires do this all the time. If one is not over the top they stay employed
So one can mix Business with Pleasure, just requires discipline, skill, and presenting ones case.
“Better a true enemy than a false friend.”