Welcome to TFP!
Everyone has pretty well summed up the reasons, I just wanted to chime in to say that there are a lot of examples on this forum dating back to the beginning that back up our opinion of test strips. Countless examples of "my numbers are perfect according to my test strips, why do I have algae?" Just as many people claiming that SLAM doesn't work when they have been at it for weeks based on test strip readings. The outcome is always the same, they either get the test kit and find they were doing it wrong the entire time, or they give up and head back to the pool stores with credit card in hand.
For a new person it might appear that this site exists to sell TF-100s. Not an unfair thought, but it is the other way around. Dave created the TF-100 because there was only one test kit on the market (K-2006) that had the accuracy to properly maintain the TFPC method. The TF-100 improves greatly upon that kit and, as mentioned above, only contains 2 color matching tests (and you don't need to actually read the OTO chlorine test, it just verifies there is chlorine). While we all push the TF-100 it is an unpaid sponsorship. We just have experienced pool management both ways, and are 100% sold on the results.