1. they do, just not very much
2. the house edge is almost twice that of any other dice site (1.9% vs 1%)
3. the maximum bet sizes have dropped off significantly
4. the range of bets available has been cut
5. the site hasn't kept up with innovations in dicing:
5a. betting is on-chain and slow
5b. bet verification involves waiting until the end of the day for the secret to be revealed
5c. other sites allow you to specify your own odds; sd still has a very limited list of odds
5d. other sites allow you to bet 'high' or 'low'. sd still only lets you bet 'low'
5e. there's no on-site chat, so there's less of a feeling of community around the site
It's hard to say which of these are most significant, but they probably all play a part. It seems like the site was just left to die, even before it was sold for a huge number of BTC.