This has been discussed many times before. The consensus was that it was too much work on the artists and that it would make us too much like other petsites. This site was never created to be a breeding site.
As to the artist work, can you imagine how much that would take. Say we have 38 different pets now, which is about right I believe. If we fused 2 creatu, that would be 38 choices for the first creatu and 37 for the second if it would look different. Then for the next breeding it would be 36 choices for something that looks different, then 35, etc. Eventually, it would be 38! (38x37x36x35x....x3x2x1) different types of pets to draw. That's 5.23022617 x 10^44 different kinds of pets. Then that times the 4 stages (we'd need eggs for all of them of course), and times however many colors there are. There would be no way for the artists to draw all that.