GMOs are typically used to grow things outside of their normal growing season, and to yield more, or was I misinformed?
The argument here is whether they're safe or not. A typical propaganda tactic from GMO companies is to redirect any discussion on safety away from the issue.
But, to answer your question I believe roundup-ready GMOs are the most typical type of crops and those are about requiring farmers to purchase expensive herbicides with questionable effects on human and livestock health.