One of the reasons why I like bicycles is that I can understand its mechanism and I can fix most of the problems myself. In my opinion, every biker should know some basics of his bike - should be able to do minor repairs and tweak his/her bike whenever needed. So, every cyclist should have some basic set of tools.
This is another reason why I associate biking with "freedom" (less dependency on mechanics).
What made me bring this topic? I have seen people getting pissed off when they don't get service from the showroom and they start writing negative review of the product/brand, which may be misleading. We have all the right to expect after sales service. At the same time, I am surprised to see some customers not able to do simple adjustments and bring their bikes to mechanics for some minor issues. I am not trying to support bike showrooms without spares and trained mechanics, but trying to make another point here.
When we buy a new bike, our expectations are high. We tend to become "emotional" when something goes wrong and write strongly negative reviews, which we later may feel like correcting, after things calm down.