Location, size, tuition cost and popularity. The regional campuses are tiny compared to tOSU and offer a few 4 year degrees which differ based on campus, but not the hundreds available at main campus. Regional students are also able to buy football/basketball student tickets. But most students that apply to tOSU as a top choice are looking for a big urban campus, so they aren’t very likely to be interested in a small campus setting.
Have you run the net price calculator for Rice? They are one of the most generous schools.
“The Rice Investment, one of the nation’s most generous financial aid initiatives that increases access to an affordable, quality education for low- and middle-income students. Beginning in fall 2019 under The Rice Investment, middle-income families with typical assets will receive grant aid to cover full tuition if they earn up to $130,000 per year, and half tuition for families earning between $130,001-$200,000.” https://financialaid.rice.edu/thericeinvestment