For people whose badge ideas get implemented.
Because new good badges are good for the SO site.
Awarding badges manually rather than automatically through an algorithm is going to be prone to chaos, confusion, and a bureaucratic nightmare for the site maintainers. Currently the only such badge is "Hacker", which is being reserved for exceptional circumstances and still has not yet been awarded.
The current reward for suggesting a good idea is increased reputation on Meta Stack Overflow. That reputation is visible on the other SOFU sites in everyone's user profile under the "Accounts" tab. I don't see a need to extend the recognition beyond that; if badges were awarded, many Meta regulars would want to be given this badge retroactively as recognition for their ideas that have been implemented.
To be very frank, meta gets an pretty heavy stream of badge suggestions as it is (in fact at one point the mods closed all the various individual badge suggestions and made a unified questions to hold them all), and most of them are not so hot. A few are decent, a few really suck, and the really great ones are few and far between.
This suggestions would magnify the scale of the sorting problem by encouraging an endless stream of suggestions.
BTW--As I count it there are 44 existing badge separate of the specialist ones (admittedly there are several groups: [nice|good|great], [notable|popular|famous] and so on). We don't lack for either numbers of diversity of requirements. So we can afford to be picky.