Rule of thumb: If its not their parents money, why should you give two shits about what they do with their hard earned cash. Theyre helping out companies by buying products.
If they worked for the money, then it's fine. I don't think my parents have ever bought a scooter part for me (other than a couple stock pro models once I broke the parts in like 5th grade).
I buy most of it myself, and get a bit for free now and then. I haven't changed anything on my scooter for about 6 months ( apart from grips and bearings )
i buy parts when they break or im mostly trying to explore what would feel or perform better. just to give me that edge. but i do give the parts time before i decide to get something else