Those badges were already set up that way previously. They were changed away from that. It doesn't make much sense to now go back and make it a requirement on badges again.
The above is actually inaccurate. I've since found Nick Craver's response about this which indicates that the badges never followed the reputation cap but have always just looked for a total of 200 rep earned on the day. The change in badge description was only to clarify what the badge actually did, and not how it functions.
Previously, they were listed as follows:
- Mortarboard - Hit the daily reputation cap for the first time
- Epic - Hit the daily reputation cap on 50 days
- Legendary - Hit the daily reputation cap on 150 days
That being said now, there really isn't any need for actual reputation cap badges. Perhaps there could be a single bronze badge for hitting the actual reputation cap for the first time, but the existing daily-reputation badges already cover this for the most part.
Badges are meant to encourage positive behavior, and whether or not you hit the reputation cap doesn't really matter when encouraging a user to continue asking and answering in a single day. The outcome for both would be the same, and I imagine the pattern for awarding both badges would be about the same too. You'd essentially be getting two badges for the same work you've been completing.