I have 2 piggies that are 1/4 cuy, they had a cuy grandmother. The male, Leonard, is a lovely boy, in his prime he was over 1400g, but his sister, less so now she's almost 4 and has osteodystrophy, but in her younger days I can well see why cuy with their typical temperaments are not a good fit to most pet homes. She was skittish, grumpy, would run and not stop...crashing into the sides of the cage, she was almost impossible to syringe feed when she reacted badly to baytril and stomped so hard on my digital scales, she broke them! Whilst I would absolutely not turn down a full cuy if they needed a home, I can certainly appreciate why some people would stay away from them.
Theres also the reduced lifespan to consider, I absolutely adore the pair of them, but they will be 4 in April yet look older and scruffier than some 8/9 year olds i've had, coming to terms with the fact they probably wont live as long as normal piggies has been difficult, especially as they're both now palliative due to osteodystrophy from also being satin carriers.