We already do our best to limit the number of notifications we send to one user by grouping badges in the same comment and we give priority to "special badges" like birthday, personal, community or contest badges.

One alternative is to make a post that displays all the people who earned each batch that day

To be honest, this won't work because:

• there are too much users who receive badges every day, and we should all expect that number to grow.
• The list won't fit on one post or comment, or it will kind of TLDR;
• newcomers do not know about @steemitboard and the badges incentive until they receive a notification on their post. That's why we receive so much reply like "Wow ... this is cool. I didn't know. Thank you".