Certs are certainly used as a filter factor and are valuable for that. Having one doesn't necessarilly prove anything but lacking one can make a job search difficult.

Another value, though, is that gaining one provides a passing acquaintance with many possibillities you may not have encountered and thus make the next job a little easier since every work site is different. In depth knowledge, though, will always come mostly from experience - best defined as "what you get right after you need it."