Not necessarily.

All clothing provides some measure of sun protection, as anyone who has ever gotten a farmer's tan can attest. Most clothing, in fact, does a pretty good job of protecting you from the sun. The clothing that has come to the market over the past 10 years or so seems to be different in only a couple of things--first is that they test the clothing to verify it's level of protection and second is that they focus on making the clothing lightweight/cool. Obviously I could wear leather head to toe and have 100% protection from UV rays, but I'd be miserable. And I can happily wear a lot of the clothing I already own and get exactly the same protection that I'd get from a Solumbra shirt, but there wouldn't be a label telling me my level of protection. The UPF rated clothes seem to provide a high level of protection with very lightweight and comfortable fabrics.

I know some of the early types of clothing had a coating on them to give the sun protection, but the coating would wash off after a while (and too soon if you didn't follow the washing instructions carefully) so I think now what we're seeing is some of the more technical fabrics being developed and used for more "normal" looking clothes that provide that kind of protection.

Sarah