1. The decision in the past was sensible at the time given what the people making that decision knew/believed/were incentivized to optimize for, versus;
2. It's worth knowing what was on their mind when they made the decision.
I think the two are independent. It could be that there is no good reason for a choice people made, but it's still helpful to look into whether they had a reason, and not just assume there was no good reason without looking into it. I personally think assuming there's no good reason for a decision without looking into it is "picking up nickels off of railroad tracks."
You save a little time if you don't try to find out whether there was a reason, and most of the time your hunch that there was no good reason will be correct. And some of the time, if there was a good reason, it no longer applies, so you are saving time not looking into that reason.
But once in a while, there was a good reason and it reflects some constraint or requirement that is still relevant. It doesn't mean you can't change the thing, but it does mean that you should address the constraint or requirement as part of your proposed change.
If you never look into the reason, once in a while you will miss something. Another comments suggested "move fast and break things," i.e. Make the change and if something breaks, fix it then. That's a strategy too, but some things don't work that way. For example, some code might fix a bug that applies to one valuable customer, and if you change the code without knowing about the bug fix, you will find out about it via an irate customer.
In some cases, the cost of an irate customer once in a while is much bigger than all the time saved not looking into things. Or maybe it's a security thing, in which case one vulnerability might be extremely expensive to deal with.
I agree with you that not all decisions made in the past are worth taking into account when making changes, but in my n=1 experience looking into things is cheap insurance against the times when there is a hidden requirement or constraint that has material impact on your business. And when I frame it in my mind as insurance, I don't mind looking into 99 things that turn out to be immaterial: The 1 time it is material makes all 100 investigations worthwhile for me.
1. The decision in the past was sensible at the time given what the people making that decision knew/believed/were incentivized to optimize for, versus;
2. It's worth knowing what was on their mind when they made the decision.
I think the two are independent. It could be that there is no good reason for a choice people made, but it's still helpful to look into whether they had a reason, and not just assume there was no good reason without looking into it. I personally think assuming there's no good reason for a decision without looking into it is "picking up nickels off of railroad tracks."
You save a little time if you don't try to find out whether there was a reason, and most of the time your hunch that there was no good reason will be correct. And some of the time, if there was a good reason, it no longer applies, so you are saving time not looking into that reason.
But once in a while, there was a good reason and it reflects some constraint or requirement that is still relevant. It doesn't mean you can't change the thing, but it does mean that you should address the constraint or requirement as part of your proposed change.
If you never look into the reason, once in a while you will miss something. Another comments suggested "move fast and break things," i.e. Make the change and if something breaks, fix it then. That's a strategy too, but some things don't work that way. For example, some code might fix a bug that applies to one valuable customer, and if you change the code without knowing about the bug fix, you will find out about it via an irate customer.
In some cases, the cost of an irate customer once in a while is much bigger than all the time saved not looking into things. Or maybe it's a security thing, in which case one vulnerability might be extremely expensive to deal with.
I agree with you that not all decisions made in the past are worth taking into account when making changes, but in my n=1 experience looking into things is cheap insurance against the times when there is a hidden requirement or constraint that has material impact on your business. And when I frame it in my mind as insurance, I don't mind looking into 99 things that turn out to be immaterial: The 1 time it is material makes all 100 investigations worthwhile for me.