I have one on my old hardtail MTB.
Yes, it is better to try and avoid potholes, and 'rig for impact', but I got caught out a couple of times and my back took a battering so I fitted the suspension post. It significantly reduces the thumps from such impacts.
Mine is a 20 year old USE Shokpost. I don't think that they make those any more but similar products are available.
Thanks to everyone who replied to suspension posts all good advice maybe I need them padded underpants , you can't always avoid pot holes with cars behind you and pushing past you keep cycling .