if every home in india has a wet latrine or toilet, it'd also mean that every home has access to piped water. if every home has piped water, it could also mean that there is less water for agriculture (from accessible surface water sources). less water for agriculture would mean less emphasis on such water-guzzling crops as rice. if there is less emphasis on such crops as rice and wheat, it'd also mean that such food- security enthusiasts as p.sainath and m.s.swaminathan would have to pack their bags and go home to obscure radio shows in america.
that could be one reason why the poor indian state can't ensure that every home in india has a wet latrine. it wants to follow the ancient prescription that the ruler/s should not harass poor brahmins.
more reasons later. meanwhile, please read this interesting post and discussion on manual scavenging.