@David **********
Since extension always is designed as an exception, thousands extensions as you claim on only 35,000 total applications is cleary a sign that the visa is not used as designed.
When they wanted the group that wants to live in Thailand on DTV they would have created a visa that is valid for 5 years where you come and go where you want and no need to get out of the country.
But that group is not the group of visitors that spend a lot.
Now DTV attracts a lot of people who want to LIVE as cheap as possible in Thailand.
The fact that a lot of them not applies at their home country, but just do some visa tourism as short and cheap as possible in neighbouring countries is a also a clear sign for that.
The intention of the visa obviously was just as you say to attract returning visitors for flexible period up to 180 days, bringing in a lot of money in periods as small as possible.
Seeing border runs as an intended thing is just $tupid, why would you send people to the border and back? What is the advantage for the country?
Borderruns are never intended, but is a loophole which occurs because otherwise you have to make complex rules as some other countries do.
There also is not one single guideline that says you should do a border run, is just is using an existing loophole, so unintended use.