Oh man. Here are several thoughts of why people give someone grief about keeping spare parts, and odds and ends.

• They wouldn't know what do to with them, and so they project their decision onto you, to not keep the parts and things.
• They don't want you to out shine them. They don't want you to do something that they believe they can't do well or at all. And so they might be casting judgement on you, to try and prevent you from doing that thing.
• They are under the influence of the general media that pumps them with ideas to just continue to consume. 'You deserve something new.' 'You don't want to deal with the hassle of repairing that.' 'It would be easier to just buy a new one.'
• They think you're making a mess or will make a mess in the future. And for reasons it seems, only they know, the keep looping this thought and feeling.
• They genuinely want to make sure that you don't overwhelm yourself with too many things to save for these random moments of need.
• They were brought up in a household that wasn't like what you were brought up in. Having boxes of things stored here and there is odd to them.

Don't let them dictate your happiness, interest or hobby. Set up boundaries with them if you have to. Tell them that you enjoy the event, experience and task at hand, and they should seek one something in life that does that for them.