Because most muslims don't even like dogs due to the nonsense story of an Angel telling Muhammad they don't visit a house with a dog in it. Arguable if they are haram or not, but viewed as filthy unclean beasts only fit for guard duty.
If you live here or have read this forum for some time you should know what cannot be mentioned. How come Buddhism does not stop all the pigs, chickens and fish being slaughtered everyday?
Our local temple has signs saying anyone dumping dogs there will be fined 40k baht, even the monks have had enough of these pests. Actually the soppy attitude towards soi dogs has little to do with religion, it's another influence.