You can't just look at data from the internet without touching it, you need to download it. The same holds true when reading data from the IPFS network.

In the process, you make it available for anyone else who ask for it, but only for a limited time; until the Garbage Collector (GC) runs. If I remember correctly, the GC run once every hour or so, so you probably won't reshare the data for longer than that.

You need to pin the data if you want to keep resharing it. This effectively tells the GC to not touch it.