If the license to lend is included in a physical copy, not in a digital, how does that explain the same pricing for either in a lot of cases. How about I buy a physical copy and digitize it, and lend it out as such? Again, not allowed, but for different rules they designed.

Rights that were acquired trough spending a lot on legalized bribery (called lobbying). Just because something was made legal, does not mean it's right or just. You only care about it being so is because you have more to gain from it.

If you have no choice to play the game, but people with more money can actively stack the rules against others, you cannot claim "utilitarian"

The IP system as a whole is rotten, and I'm talking broadly here: music, patents, copyright, academic publishing,... IP protection is necessary, but as it is now, it's built on rules designed by companies to further their interests, not to serve the intended purpose. While it's riddled with protections for them and not for the others. While copyright and patent trolls, misuse the system to deny others theirs. And this is another one of those situations.

How is lending a physical copy different from lending a digital copy?

Just because the industry decided to consider digital both digital and physical at the same time does not mean it makes sense. Just because they lobbied to limit the scope of digital copies to be way more narrow that what can be imposed on physical copies?

Some sell digital copies at the same price as a physical copy. But unlike the physical you only rent it, not own it, since it's only a perpetual license at best. In case of some DRM only until they decide to pull the plug on whatever online DRM service they were using. Then you are stuck with a bunch of one's and zeros you paid full price for, but can never legally access.

Just like they consider every pirated copy of a digital IP a theft of a full priced physical item while it is just a license violation. You can't have it both ways.

Think about it this way: a library is offering a service to make books available at a fee as a social service. They've been doing the same for decades with physical copies. Just because of the greed of publisher, this should not be allowed anymore for digital copies just because they decided so cause they could make more money?