Though they don't, in my experience, ask for any indication that this comes from a prescription, that it's up to date, etc. You're free to use numbers from an ancient prescription, just guess at your refraction, whatever.
Some other online glasses sales places will make you show them a sufficiently-recent prescription.
Any store will sell me clothes that don't fit, food I'm allergic to, and chemicals that are dangerous if used incorrectly. It's not unreasonable to expect the buyer to take some basic responsibility.
They have their limits to this laissez fair policy though, for whatever reason...I tried buying multiple pairs of glasses at slightly different strengths from Zenni (stronger rx for it for outdoor distance views and weaker for inside and they freaked out and they called and asked if it was a mistake. When I explained what I was doing, they said nope and cancelled the order on me.
Some other online glasses sales places will make you show them a sufficiently-recent prescription.