That’s not just the LHC - it’s pretty common across high energy physics, nuclear physics, and astronomy, at least.
It’s a pretty great fit for the technology. You keep the most recent data on hard drives for analysis, and as new data comes online, the old data goes to tape. You don’t want to get rid of the old data, of course, because you need it for analysis verification and when people come up with new analysis ideas, but the older data naturally gets accessed less and less as time goes on, making tape storage a natural choice.
It’s a pretty great fit for the technology. You keep the most recent data on hard drives for analysis, and as new data comes online, the old data goes to tape. You don’t want to get rid of the old data, of course, because you need it for analysis verification and when people come up with new analysis ideas, but the older data naturally gets accessed less and less as time goes on, making tape storage a natural choice.