Snort has been far more than a network "grep" tool for many years.
"Grep" refers to the Unix utility used to identify strings in content. Snort can indeed identify various content strings via direct traffic inspection. However, Snort has far more powerful protocol analysis and traffic reconstruction capabilities that don't get as much press as its signature matching engine. Snort won't necessarily meet the needs of all clients, but anyone who wants to collect indicators of suspicious or malicious activity will find Snort exceptionally helpful.