Apart from having MTS (5 aqauriums) I have one female cat (spayed), One male canary, guinea pigs with babies and a dog.
Why do I have them, the cat keeps the field mice and rats out of my house, the canary is a pleasure to listen to when I don't want to listen to music, the guinea pigs were found in my back yard, nobody claimed them so I kept them and the dog helps to keep me fit.
And the fish are great to watch when there is nothing on tv.
Apart from that I guess we all have the same reason at the end of the day, (love animals)