'Zactly.
I'll admit that I've been doing just that. Buying Creatu and then releasing them after I scan them. But, without meaning to boast, I have plenty of TU to spare. And it'll be worth it when I sell or trade the Ivik eggs I buy. It's worth the loss for the overall gain. Not only that, but the majority of pets I attained - found in the Forest - had truly terrible names. I'm not going to keep a natural Sirleon called yyyyyyyyyy because I feel sorry for it. Who on earth would want such a Creatu? Truthfully now. How many of you would resist dyeing/beaning and renaming that Creatu? And devote your time to feeding it and keeping it on your profile forever? Truly?
I can understand your frustration. But guys... these aren't real animals. They're pixels and data. Numbers and coding. We only feel sorry for them because part of their existence on the game is a pretty 2D image, and because a member of staff went to write up a bit about their nonexistent biology. I only get angry when breathing, bloody, warm animals are misused and abused. But in a virtual pet game? As long as you don't try doing the same thing in real life - which is an evil and selfish thing to do - then you shouldn't feel shame for using digital data for your own personal gain. You're not hurting any living individuals, so why fuss? Make a distinction between real suffering and virtual "suffering".
If you sell something in your ranch, you can't dictate what the buyer does with the pet. This isn't real life, where you assess the future owners of your stock. If you're that desperate to make sure your Creatu has a nice time on someone's profile or in their Showroom, then sell them selectively.
By the way, I'm just voicing my opinion. I am not making out to offend or belittle anybody.