To play devil advocate, watching tape is always an advantage but maybe not worth it for many people. It seems like a ton of people mostly live bet, maybe 2/3 of their total on an event is through live betting. Except for debuting fighters you pretty much know fighter A or B has the best cardio (for live betting) or they are about even. After that you are trusting your eyes watching the fight (even for cardio). AlsoI find people watching tape have a pre conceived notion going in and just look to verify that notion even when maybe it is not there sometimes.
If you love watching tape or get a lot out of it and make a killing on pre fight bets, that is great. For some, the time spent doesn't equal the benefit. Some people have an amazing recall of past fights without re-watching (I'm not one of them unfortunately) and sometimes those impressions are valuable. Watching a fight when you know the outcome is a different view from watching it live for me - sometimes the live feeling is a good takeaway too). For example re-watching a fight that went the distance, a near sub finish or when someone gets rocked seems kind of minor while watching it live I was on my feet looking for the finish - I'll remember that from the fight. But on rewatch, I'm more A won round 1, B dominant round 2 then fighter A took the 3rd round and kind of discount the near finish (maybe people are better at re-watching then me)