They touch on it with the point that alcohol and other drugs make you feel good, but i think there are other practical reasons:

• Psychedelics take a lot of time, usually at least a few hours up to days. Yes you can smoke dmt and it's only ~15 minutes, but it's not very convenient or socially accaptable to pull out the pipe for it (this might be changing with dmt vapes)
• more work needs to be done to ensure the experience is safe
• they're not super easy to find, especially not safely. I'd be interested to see stats like the one highlighted in the article for other illegal drugs
• they're not chemically addictive
• they don't seem to directly/reliably enhance productivity (e.g. caffeine or nicotine), socially lubricate (e.g. alcohol), or chill you out (e.g. weed)