Good question Luker, I'd be interested in the answer if anyone is able to provide it. My only rationalization is that the risk is substantially reduced when leasing rather than owning. It would be the responsibility of the owners of the drill to ensure reliable drilling equipment while allowing NOT to focus on the business they do best (finding areas to drill).

In some cases (oil & gas) some of the large integrated companies do own and lease out drilling rigs. This came to be a few years ago when oil prices went to approx. $150/bbl and companies were having issues leasing these rigs as they were so high in demand. Back to your point, how much drilling would warrant a company going out and buying their own drills and in what environmental conditions. I'm people here much smarter than I could help answer that question.

Cheers!

Goldhaven