The high volume growers may be afraid of losing bargaining power in control of the pricing.
Lets say someone introduces a manufacturing and distribution model that brings the going rate for the equivalent quantity of a carton of cigarettes (8.0 oz.) down to the similar price range. With RYO operations, you can get loose tobacco custom blended and machine rolled for $25.00/carton, or just the loose tobacco for $15.00.
Now I could be outdated, but last time I checked (16 years or so ago), non-hydro in bulk quantity was about $100.00/lb. or $75.00 for 8 oz. if you maintain the quantity similar to a carton of cigs. To bring it down to even $25.00/8 oz. would be a 66% reduction in price.
To be competitive and allow for retail mark up to $25.00, it would have to be sold in bulk at probably 50% less, which would bring the wholesale price down to about $12.50/ 8 oz. or an 83.4% reduction.
So, sure the farmers that currently grow it have a lot to lose if a major player in the tobacco industry (who already have all of the technology and distribution channels required to do something like this) comes in and retools the working model that they already have in place to a more market friendly/retail type of distribution system.
...but that is based on old price/quantity. I have no idea where it is at now, but like everything else, has probably gone up.