What's up with lousy bass on classic rock recordings?

You are correct there is no low level sub bass in older hard rock. I’d say it’s not much below 80hz. Try recordings with a prolific bassist like Phil Lynott, Jack Bruce, Felix Pappalardi etc. Or Beatles - Come together. If you are running Roon there are 779 recordings of Come Together to try :) Musica Nuda makes a fun version.

I think it may be the recording or even desired sound - I have Boston, LPs, DSD files and can stream lossless and they sonic characteristics are very close yet Boston doesn't have the bass line of Jazz I listen off of Linn Jazz.

There was a lot of variation on LP pressing in the 60's, 70's and early 80's. There was a bunch of different pressing plants just within the USA and there could be a number of reissues the same year as the original release and up to 10 years later due to the large volume of sales. 

I find most of my earlier LP pressing to have a more balanced mix than some of the remasters today but rarely lacking on the bottom end. I have some fantastic new pressings from Analog Productions and MFSL and also remasters from some of the original labels like MCA and Columbia but I do find some of the new remasters to be a little heavy on the bottom end. I'm sure a lot of people like the amped up bottom end but I prefer the more balanced attack of the old original pressings. It's all a matter of personal taste in music. 

Many rock recordings of that era are quite poor - others are quite good. But yea, lots suck.  Many many reasons, one famous one being that several of them were going deaf with traditional old male hearing loss, accelerated by their jobs. Pete Towshend was afamous for over-riding on mixing -- balancing what HE heard. 

Many are also heavily compressed, and the house sound was achived with mix after mix, so you have a 27th generation tape in effect.  Not exactly audiophile purity.

On the other hand, listen to LA Woman, or much Bowie - surprisingly good.

I've noted many times that a huge advantage of streaming digital is that you have access to remastered copies of great old, rock and pop albums. Wile they are not perfect they are all much better - and often that trumps any quibbles you may have with digital. Certainly it does for me - big time.  And i have some VERY good vinyl gear.

The best recordings remain purist.  3 mics and no mixing to speak of. Verve, some lue note, mercury LP etc.  Those are the polar opposite of most rock mixing and production techniques. After all, George Martin was the 5th Beatle.

G

It all depended on the recordings. Tying all classic rock into one lump won't do it justice. Prime example Tommy Bolin's Private eyes and Teaser, both vinyl from the mid seventies, if you can find better bass anywhere, in any genre, or any period, I would like to know about it.

However the majority of BIG classic rock bands used very average recording methods back then since their name alone was enough to sell records. I find the lesser known bands went much further out of their way to hire better technicians  to get a better quality sound in hope of being discovered. And it is a good thing for me since most of my collection is off the mainstream bands.