[DonRotolo]

Rivets are weak in shock load, but great for static loads.

A loose bolt is much weaker under cylical loads than a properly tightened one (ask the Mech Engineering guys why). A rivet (of the type you are considering) cannot be 'tightened' - the tightest you can get it is not very tight. (Rivets for big steel, like the GW Bridge, are installed hot, so they shrink and 'tighten'). So, loose rivets and cylical loads equals premature failure.

Also, the rivet starts to get loose quickly, and it's ability to be strong* drops significantly. That means instead of tightening up nuts and bolts, you get out the hammer and tighten up the rivets.

*Strength doesn't actually change, but a loose member has a little bit of distance available to allow it to build up some momentum before it hits the end of the rivet...and that isn't good.

Don

[Edit: The above refers primarily to standard peen-over rivets, not Pop Rivets mentioned by Deepwater]