I'm guessing to save space. You still need a toilet to take a shit.. why have urinal if toilet can perform same function? most bathrooms are already small as it is. If you're a female, it would be completely useless so it would only be desirable to 50% of home buyers anyway
I've seen one in a house before. Was a pretty massive house with both a urinal and toilet bowl next to each other in the toilet room. I guess this is the only time you'd see it. Would be kind of pointless having just a urinal which only 50% of people can use. I bet there have been a few urinals on MTV Cribs...
Urinals are used in public for efficiency and they are space savers. But in a private home, it's the opposite. Why do you need a urinal if a toilet does the same thing? There's only one person in your house bathroom at a time.
Plus, like someone said, it would be kind of gross to have a urinal in your house. They smell and splash urine.