There are several reasons:
1. SE Nuke is a monthly subscription. Unless you are cranking out sites each day, at some point it is just sitting there and you do not use it. I started cranking out sites each day, but at some point I had to stop because the numbers got unmanageable. I could not coordinate link building in any coherent way because each site had 5-15 terms x 20 sites etc its easy to see how it gets out of hand. That and you have to do it over time or they get sand boxed. So I cut back and stopped new sites, cut some out and worked on my existing. To go over time there were periods of time where I did not even use it. If I could pay someone to do it only when needed, that is very beneficial.
2. Time. SE Nuke is automated, but you have to babysit it to a certain extent. You have to create the accounts (this takes most of the time), then spin article, load it up, put in keywords etc. For a single site this is easy, once you get 10-15 or even 20 sites the time factor becomes and issue. Outsourcing is the key to really growing your business. If I had 100 sites, there is no way in hell I could use SE nuke to build them - there is just not enough time in the day for a single person to do that. So a service like this would be great.
