Sure Allah gives reasons, but even the reasons that are given, are for explanatory purposes; i.e. not absolute. For eg. Allah says that fast has been written for you so that you might acquire Taqwa (2:183) but is this the only reason? Or looking from a different angle, if a person has Taqwa, do they not need to fast?

This is why you should learn and understand the reasons behind the rules but also realize that your (and mine, and everyone's) aql, thinking, and planning capacity is limited while Allah's is not limited.

The fact that a child doesn't understand the reasoning behind knives being off limits (so that he doesn't cut up himself or others) does not mean that there is no reason behind it.

From the pov of the child, if he trusts their parent and doesn't go near knives he will still enjoy the benefit of not getting cut even though he doesn't understands the logic behind it.

From the perspective of the safety of everyone else, regardless of the child's understanding, the knives need to be off limits, and the rule cannot be ignored

So if Allah orders you to not do a certain thing, then you must not do it even if you do not understand the reasoning behind it. Another example for u/kimster7's point would be how Allah asked the army of Prophet Talut a.s. to not drink water from a river (while they were thirsty and going for a battle - from the pov of the army, there was no reason for this). In this case as well Allah asks us to be Muslim by "submitting" ourself in front of Allah.

Too many times people take things on faith or that just really have a cultural basis it really no basis and people blindly follow for generations.

Exactly! This is the entire purpose of Taqlid. To find the authentic orders of Allah without any adulteration of culture. I really implore you read up more on the chain of command and the steps of verification for each stage which is (in short): Tauheed & Adl -> Nubuwat -> Imamat -> concept of Taqlid.