I have not looked, but I bet anything that I was putting money that would have been taxed at 15% (and maybe less) into these accounts.. I did pay 28% when I converted them to a ROTH when it first came out.... not sure in the end if I paid less or more taxes than I needed...
I thought that may have been my case too, but when I checked tax rates from when I started my 401k that wasn't true.
https://www.scribd.com/doc/190499803/Fed-U-S-Federal-Individual-Income-Tax-Rates-History-1862-2013 shows historical tax brackets. There were a lot more tax brackets back before 1987, if that's when you started, and the rates in general were higher, especially if you didn't have any tax shelters.
I started contributing to a 401K in 1984 or 1985. Remember that the deferred money is taking off the marginal (top), not your effective (average) tax rate. If it was a partial year of full time work in 1984 I was on the 23/26% border, then 30% the next year, plus I was only deferring up to my company match, so I feel good about the early deferrals. If you want to convince yourself you can check your SS wages against that table and see what you really deferred at.
Nowadays, with the bigger 15% bracket, I'm advising my son to only defer up to the company match, and contribute to a Roth after that.
28% might be a high conversion rate compared to partial conversions at 15%, but if the investments have done well in a Roth, you aren't paying more taxes on them. Also probably not all of it was converted at 28% unless you were already in that bracket. I remember when someone said they did a full conversion in the year when you could defer paying the taxes by splitting it over the next two years. They did the math and figured they came out better by paying the higher taxes and having the nice growth that followed tax free, rather than having most of the money grow in the tIRA and pay taxes on those gains, even though it would've been a lower rate.
My motto is that if you made a mistake in the past, and it's too late to fix, learn from it, make the best decisions moving forward, and move on. No sense beating yourself up. If someone today is maxing out a 401K in the 15% bracket, the best decision moving on may be to reduce contributions to the company match, put the rest in a Roth and possibly a taxable account, and consider converting some of that 401K to a Roth if that's possible.