Floyd has recently made going undefeated become the end all and be all of a fighters career. Imo going undefeated isnt that big of a deal because guys now duck or rarely fight each other to avoid not going undefeated. I think Ls to bad opponents will definitely tarnish one's career, but a dude who has 2-3 Ls agains top top competition and managed to beat those same guys in rematches is just as good as a dude who went undefeated. (This is not an attack on Floyd, but more of just another way to look at things)
Having that 0 is a nice promotional tool on the way up but I think once you're up at the top level and consistently fighting the best it becomes less important than who you face and how you overcome adversity should you lose the 0.
It's great when you need to sell and hype a meaningless stat to casuals who'll buy any crap so long it's fake gold plated...
Like everything, numbers need context. Nothing wrong with losing to elite competition, though. Save for Ward, Marciano, Lopez, Mayweather, McFarland, Calzaghe, etc., everybody takes an L here and there. Going 35-0 and never beating a P4P fighter or top contender is less impressive than somebody who goes 40-5 with some wins over HOFers and a handful of wins over P4P fighters, who only lost to fellow elites.
Losing is the worst possible outcome in every fight. Winning is important; the goal for each match. Being undefeated means you beat everyone you fought. If you fight multiple ranked fighters and remain unbeaten, that is mighty impressive. A given loss can lift a legacy and can be an accomplishment depending on circumstance. But what would lift the legacy better? A win in said fight.
It means nothing or few. Wilder knocked out a lot of bums and was undefeated before Fury punched him twice.
In a sport like boxing, where, by and large, you choose your opponent, undefeated is often more a product of who you fought as opposed to a measure of greatness. Sure, the ultimate would be to win all fights AND fight all the top challenges of your era. Unfortunately in most cases it becomes an either/or thing.
Going undefeated as a prospect is one thing. Going undefeated as a five-time lineal champion is...certainly another thing.
To some they lose confidence as soon as defeated. Take Bute. Was never the same after Froch. So maybe for some without mental strength it's important. Losing didn't seem to affect Froch though
Ray Robinson was better than manny and floyd combined, so the 0 isn't everything To be fair it was the zero that made Floyd mega rich. People paid to see him lose