I thought it was more to do with improving the overall standard of life. Horseshoe design means the patient can taste the food alot better and can feel the texture of what they are eating and drinking plus it has a massive effect on phonetics.
It would be the best, but some dentures are attachment supported prosthetic and some are tissue supported attachment retained. In the case of a denture the more tissue coverage in general the more stable. I have some upper dentures that are like lowers with no attachments and the patient makes it work, I have some spherio flex that have 4 implants and the patient required a full palate to replace missing bone & tissue.
It is a matter of patient expectations, abilities and comfort. K2 an implant bridge does not always have only teeth sometimes a certian amount of pink is required, with removable a cast frame might be nice but may not meet the patients desired cosmetic, or implant availability.