I try to use nothing except solid hardwood floors in my rentals (except for the tile in the bathrooms). I'm happy with the performance in single family homes.
Tenants (and buyers) favor it. I doubt it makes any difference in the assessed value of the home, for equity / financing, but it does make the home more desirable to tenants and buyers especially IF you are in a B market or above, and it is done tastefully (no tiger stripes). Hardwood certainly factors favorably into the capital expense figures, because it typically lasts a lifetime.
I have rented one of my houses for 20 years and the wood is still in acceptable condition. The oldest wood was originally installed in 1911. There was some 30-year old floor from when I purchased the house. And we put hardwood in the kitchen 10 years ago. It's all still fine unless we get pets with nails scratching it up. Occasionally we spot-sand.
We source hardwood as close the the woods as possible and usually manage to pay under $3/SF for the raw material plus staples and other supplies. It's economical and beautiful if you purchase unfinished hardwood and install it without modern pre-finished microgrooves that trap dirt between the planks. It will last a lifetime, and turns out to be cheaper than a lot of other surfaces, including most tile and carpet.
My husband and I have learned how to install it. We sand and finish new hardwood floors with a water-based polyurethane satin finish. We can turn the house over to new tenants usually with just a good scrubbing.
Hope this gives you some idea under what conditions hardwood may be "worth the investment"