[tharkun__]

I used to use a lot of direct language and I've switched. I think a lot of it has to do with whether it is done in person, where you have intonation and body language to interpret. The exact same question can be taken in totally different ways when only in writing, especially if you've either never met someone even over video or you've not had the best first experience with them.

To take the example from your parent, some sort of problem where you had to choose an algorithm to solve some problem. There are multiple choices that have their pros and cons.

    Mh, very interesting! Why did you choose that algorithm?

Imagine this in person. The "Mh" comes out finger placed on mouth, thinking and exclaiming an excited "Very interesting!" as he has some realization from thinking about it. Then, with an excited face expression and in a tone that signals he is interested in comparing notes asks the "Why did you choose that algorithm?" question. Totally OK. You now go on to discuss the pros and cons and why you chose that particular algorithm over another one.

Now the very same one:

    Mh, very interesting! Why did you choose that algorithm?

Imagine this either in person or in writing where you've had previous "run-ins" with the other person, so you imagine it like this: The "Mh" comes out scoffing, almost barking. A mischievous "very interesting!" that transports his contempt for your choice. He knew you'd make this totally inadequate choice of algorithm even though better ones exist. Followed by a condescending "Why did you choose that algorithm?". That conversation is dead Jim!

The point after all this being that the word why can very easily be interpreted this way, which is harder to do when using these other words in part also because you have to structure the sentence in a less 'violent' way.