Custom-designed or heavily modified buildings tend to be quirky; they are designed around the particular tastes and requirements of the previous owners. Generic houses are more one-size-fits-all. They may not fit any particular person as well, but you know what you're getting and there are certain baseline expectations that won't be violated.
To some extent, people actually will pay for quirkiness. It can be easier to find a home you love in a neighborhood with a mix of houses of different ages and styles and owner-modifications. Old houses can be more valuable partly because they've been modified over the years to be more livable. But for houses that are farther from the norm, it's harder to match the right house to the right buyer.
(I say this as the owner of an 80-year-old house in Seattle with some very odd changes made by previous occupants.)
To some extent, people actually will pay for quirkiness. It can be easier to find a home you love in a neighborhood with a mix of houses of different ages and styles and owner-modifications. Old houses can be more valuable partly because they've been modified over the years to be more livable. But for houses that are farther from the norm, it's harder to match the right house to the right buyer.
(I say this as the owner of an 80-year-old house in Seattle with some very odd changes made by previous occupants.)