I know you know a lot more than me about playing tennis, but I disagree. Continuing to play can severely worsen a lot of injuries. And does the crowd really want to see a limping, in pain opponent lose easily? People just complain of retirements more in tennis as injured football or hockey players can be easily subbed off.
Well yes no one is in someone else's shoes and it is difficult to ascertain. But in my opinion, no matter how bad the injury is, one must play on. The crowd would rather see a man play it out like a warrior than throw in the towel, I guarantee you that.
You don't have to run around like a rabbit, you can't if you are truly injured, just let the guy hit some aces, throw in some serves and boom, it is over in 10 minutes. Who knows, maybe the injury will get better, the other guy will choke a bit? This has happened.