Unless you're truly an elite talent - PDW, Walter Ray, PBIII, etc. - it mostly comes down to whether or not they think that you can help them move product. This isn't to say that they don't want you to be a good bowler because that certainly helps too; however, they'd be likely to take a 190-average bowler who owns a shop and sells tons of balls than a 220-average bowler who doesn't.
As such, if you want to get on staff, you need to show them that you bring more to the table than just a high league average and a bunch of honor scores. You need to bowl a lot events (leagues, tournaments, sweepers, PBA, etc.) to keep their products visible. You need to show them that you are well-respected, polite, professional, and approachable, not some egotistical hot shot who nobody wants to talk to. Again, if they're going to do something for you - provide you with balls, bags, team support, etc. - you need to show them that you can represent their brand in a positive and professional manner that makes people want to use their stuff.