Ask HN: Is it normal for tech companies to test for drugs?

I'm an engineer at a small-to-mid size Bay Area software company that recently began rolling out a drug testing policy.

The policy is to perform "random drug testing on a regular basis" as well as testing any employee "reasonably suspected of using illicit substances". The messaging we're getting from senior management & HR is that this is a normal thing for a company to do, and is part of becoming a mature company. This strikes me as odd and not true, but I haven't worked at that many tech companies. Is this a normal policy in the industry? Is this a huge red flag? I'd love to hear input from the HN community on this.