With textlogs you have a hard time noticing a couple of added/removed/changed characters or even entire log entries. Thats exactly why some industries may not use text logs in the first place as permanent records that are at least temper-evident are mandated.
If binary logs go kaputt they tell you exactly which entries were effected and still display every bit of data they contain. Typically you do not grep in binary logs: Grep can not make sense of all the extra data in the logs (way more than in a typical syslog), so grep is just a poor tool for the job. You typically can use grep as binary logs so contain lots of text. This is ignoring compression, encryption and other extras of course.