3) If I remember correctly, (possible I am wrong because I am going by memory on something I read a couple years ago) most arrested and sent to prison the last few decades are dealers or large growers. (over 4 plants, the recognized personal number in most states)
Until you can provide sources, what you say has about the same value as a used sheet of this:
As for why the government fights it, they spend far more then they make from it.
Not counting asset forfeiture.
Current asset forfeiture laws only require the accusation of a drug crime in most states. No criminal conviction is required, and even if a criminal trial returns a not guilty verdict the burden of proof that the property was in no way related to drugs is on the defendant.
In federal cases, OHP received nearly $8M in funding through civil asset forfeiture equitable sharing with Uncle Sam between FY2010 and FY2012 (up to 80% of seizure value, depending on what agencies - state, federal, and local - were involved). They also illegally spent ~$1.8M of that money.
OHP's budget for law enforcement activities during that time period was ~$300M.
That does not include cases that do not involve Uncle Sam, and those go 100% to the agency bringing the case. To give you an idea, in that 21-mile stretch of I-40 that goes through Caddo County where you always see interdiction teams, overall $1M was seized by a private contractor through July. That does not include the amount seized without the private contractor. For what it's worth, I hear from several of my lawyer friends that deal in either asset forfeiture or criminal defense that Beckham County has an even higher rate of forfeiture and arrests based on questionable stops (but it's not "newsworthy" because it doesn't involve cronyism). I'd love to find a comprehensive data source of asset forfeitures by jurisdiction, but odds are that will never happen considering that many of the municipal cases take place outside of courts of record.
By the way, in some states, a "secret compartment" means you're trafficking drugs, even if there are no drugs to be found, regardless of whether or not it is a factory feature.
I know some police departments that would likely have to shut down if it weren't for asset forfeiture, federal and state drug war funding, and federal terrorism funding. No one wants to be the recipient of the political poo flinging for costing cops their jobs.