Traditional background checks are very blunt tools, where decisions are very binary. If an individual is a felon, there is typically zero room for negotiation. This is often the case even with just a misdemeanor. There is usually very little trusted, low cost, easily accessed data, which can balance out or provide a more nuanced view. A service like Checkr is able to provide a much more comprehensive picture, with more depth and nuance, so that employers can be more discerning and less binary.
Also, it's not as if applications don't already specifically ask for information on criminal record. The standard is that employer has this information, without doing any actual background checks. I imagine a comprehensive background checking service would mostly serve to incentivize an employer to hire a subset of previously convicted individuals that they otherwise wouldn't have, and not the other way around.