Varies a lot by school. The very top high academic D3's tend to offer NO merit money, make need blind admissions, and pledge to meet all demonstrated financial need. Lesser academic schools that are in a a feverish competition for the best students, offer lots of merit money. Merit based scholarships are essentially tuition discounts. They are used to attract better quality students. Some small "liberal arts" schools are so desperate for students, they will offer "merit" money to pretty unremarkable students. Many fail to meet their admission quotas from year to year. Others are less desperate for students in general but are desperate to attract the top of their admission pool.
So what counts as "meritorious" varies a lot from school to school depending a lot on their competitive advantages or disadvantages.
There are also special talent scholarships -- usually they come as the result of some competition. But athletics does not count as a special talent in this sense.
Also, some schools make it clear up front that they will NOT increase merit aid in response to better offers from others schools. Others may.
Bottom line. It's very much a school by school sort of thing. Hard to generalize except to say that at the very top of the High Academic chain -- where acceptance rates are in the single digits and yields are 75% or higher and endowments are large -- you will not find a lot or any merit money being doled out at all.