One flat is an accidental puncture, 2 flats is a pattern. While I always check for protruding glass or spokes when I fix a flat, if there is a second on the same tire/tube there is usually a root cause that can be fixed. Sometimes the tire itself needs replacing, sometimes the rim tape, sometimes it takes a little blood from rubbing your finger inside to find the piece of glass. Lots of reasons but eventually you find it, sometimes the hard way.
The way to prevent flats is to buy a lifetime supply of patches, cement, valve cores and spare tubes. You'll never get another flat. Also, never talk about never getting flats...