You can imagine that street food doesn't earn both the vendor and the state a lot of money. Every country wants to climb the socio-economic ladder. And part of that is moving to higher end service industry with larger profit margins.

Removing semi-illegal street food trucks that operate without abiding by food safety laws, pay taxes (?) or invest in the local community by buying a building, hiring a staff etc...

Without this, decent restaurants don't stand a chance. And in the long run, that is bad for the people living in bangkok.