Do you have any data for this? The only source[0] I have been able to find easily with numbers says about 30% of beef is non-factory farmed.

For every other meat type, it's overwhelmingly factory farmed (98%+).

0: https://www.sentienceinstitute.org/us-factory-farming-estima...

That is, admittedly, a lot higher than I was expecting! But 70% is still a sizeable majority. Moving the entire industry to grassland feeding would likely result in a fundamental upwards shift in how beef is priced, one that I suspect the GP would be unwilling to accept.