Allow me to throw in an interesting proposition's. Why date a Pokemon when they don't have any really interesting or relatable past? Humans have childhoods, teenage years, adulthood, etc. and have experienced a lot of things that you could reasonably relate to as a person thus making a relationship more believable and also not boring. Pokemon on the other hand live in the wild without a lot of stuff that we as humans can relate to.
Now yes, Pokemon can get experiences and learn a ton, but those would be experiences you gained together, not stuff that you've experienced separately. Don't you think you'd feel like your in a relationship with a person who lacks experience in life?