Did season 1 and 2 not sell very well?

The long gaps between the different seasons being released has led me to wonder if neither one of the first two seasons was particularly successful when they were released on DVD. According to Amazon, season 1 was released on March 22, 2005 and season 2 was released on June 12, 2007. Now, a gap of over two years in between releases seems pretty extreme to me. Perhaps, knowing that they only had three seasons to release, Universal decided to stretch the series out as a way of building anticipation for the release of the second and third season (kind of like Disney releasing their animated classics once every seven years to build demand and anticipation for the next release). That’s my optimistic opinion. I feel like a more realistic point of view is that the first season didn’t sell as well as Universal was anticipating. Perhaps this made them hesitant to release the rest of the series, and the only reason they ended up releasing season two was to see if sales would improve. Perhaps they didn’t, and that’s why it took almost six years for season three to come out (not to mention the fact that season three was released by Shout Factory instead of Universal). Maybe Universal just didn’t see enough success in the first two seasons to justify the expense of releasing the final season and if it had been up to them, season 3 would have never seen the light of day. Thank goodness Shout Factory decided to release the third season themselves. Anyway, that’s my guess. What do other people think?