Has anyone noticed?

[SweetPea]

Willie Pep went 62-0 before losing, then won 72 straight before losing to Sandy saddler, thats impressive!

That's why Willie Pep is a legend, and we'll never see that kind of record again. These guys were fighting far more often than the ones we have today, fighting 2 or 3 times a year, simply because the promoter in those days would take far more money, and even when they reached contender status they wouldn't be making too much money. At the end of the day, money is what makes fighters lose the hunger, and you can make enough to retire on at the top level in 10 fights these days, look at Floyd Mayweather, no point doing something that will get you seriously injured for more than you have to.

Willie Pep is certainly a legend, and his record is incredibly impressive, but sometimes it's dangerous to put too much value on the number of wins that these guys piled up.

If you look at the records of older fighters like Pep, or someone like Duran from the 70s, they didn't defend their titles any more than the current guys do.
They would defend their titles against top contenders 2 or 3 times a year, just like today's fighters do.
But in between those title fights, they would fight 2 or 3 non-title fights against total stiffs to pick up easy paychecks.
Here are some of the records of the guys Pep fought during that 72 fight streak in his prime:

2-3
1-4
11-6
16-15
37-27
16-8
10-9
33-30
25-25
17-11
14-17
26-28
16-34
30-32
25-35
28-32
14-19
29-15
29-33
8-5
20-15
20-40
31-22
31-39
33-23
5-6
9-18
19-16
4-8

[THE THIRD MAN]

The answer to this is pretty obvious.

It takes about 30 fights for a fighter to establish himself as world class, at which point he starts taking on a higher level of opponent.

This is the best answer on the subject and the correct one.
A lot of fighters rack up 30-40 undefeated fights on their record then meet a better class of opposition and move up weight divisions, it's only a matter of time before they encounter a fighter whose style will
not suit them. Forrest V Mosley being my example. Mayorga V Forrest being another.
Once a fighter has established himself and becomes a World Champion every fight he has from then on is usually against a top ten opponent, you can't win em' all.