Also in other countries (like Canada) police don't even care about drug use as it's not illegal. So purchasing grams of a substance wouldn't even be worth a raid as they'll not find anything to charge you with and the fallout would be greater than the reward.

The political fallout in Canada for running a raid where nothing is found is massive. Warrant mistakes have landed police agencies on the front pages for weeks, if it came out they were doing raids based on next to no police work, not only would the police be under fire but the judges would be too.