Clay, it is very common among certain circles of teenagers. It was one of my biggest ongoing battles with my DS1, a few years ago.
Some parents certainly do not ask at this age, and some ask and happily accept lies. I once discovered that my DS1 (then 15) and two of his friends were not where they had said they were - the address was a false one - and after I had picked them up and given them a bollocking, I let the other mothers know. They clearly thought I was totally mad. One said to me blithely "Oh he never tells me where he is, so he's not lying!"
I do think drug use is part of the reason for secrecy, I'm afraid. I also think you're already doing the few things that you can do about this.
(I also stopped all money, but there is always someone with a fiver to buy a few cans or a bit of weed. Grounding is not possible: if they want to go out, they simply go: mine climbed out if the window without his shoes, the last time I tried it. Involving the police is counter-productive, IMO. If they don't take action (which they probably won't, unless you have actually got hold of the drugs and insist they arrest your DC) it reinforces to your DC that they can get away with a lot of drug use. And if the police do take action (which they will for 'hard' drugs and dealing) then it gets your DC a police record that will affect future jobs and a fair bit of kudos among his friends, and pushes him further into the company of people you want to keep him away from).
I never found a way to guarantee I knew where he was. In the end, I settled for always having a second emergency contact number that was not his mobile. I 'trained' him to give me this by calling all his contacts if he didn't give me one, which was of course embarrassing. But I rarely had an emergency, so I don't know whether some of the numbers were false too.
They do grow out of this need for secrecy. At 15, they seem desperate for independence, and they're afraid you'll stop them, so they don't tell you. At 18, they have much less to prove, and they have more independence. My DS now tells me where he's going, without prompting usually, and always when asked.
I would caution against encouraging him to bring friends home now, tbh. It was my preference too, and I did at first, and he did occasionally... But I overlooked the fact that it is only a good idea if you're sure he has 'nice' friends. Now your DS has got in with a druggy group of teenagers you don't know (as my son did) it is, simply, too risky. I had things stolen, and ultimately I was burgled. After that, I put a total ban on friends in the house for a while, and a permanent ban on anyone I hadn't met and approved.
This was the worst, most stressful period of my DS's life for me, so you have my sympathy clay. The good news is, so long as he stays interested in academic success, and/or other positive activities, he will probably grow out if it and get back on track, as my DS seems to have done. :)