There are two types of Bitcoin Holder,
1. Short-term holders - those who usually sell their coins and empty their wallets.
2. Long-term holders - those who usually hold for many years and see their wallet address filled with a lot of Bitcoin.
Perhaps, it was their choice and you know what, it was hard to convince a person to hold when in their mind is to sell when the price went high. You can't force someone to hold if it was not in their mind.
Ultimately, everyone has their own perspective as to what to do with their Bitcoin. I have found that people who don't have money worries are considered to be holders compared to people whose savings, or better yet, life savings are in Bitcoin. This category of people would always have to spend their Bitcoin to cover their needs and that's perfectly fine like you already said. There is no one-size-fits-all for this sort of thing.
I couldn't find a thread for beginners, so I'll ask here with your permission. What advice would you give to a beginner who wants to be knowledgeable about cryptocurrencies? Where to start?
This forum is a good place to start, it's a knowledge gold mine if you do know where to look. you can the search button to find aged discussions but if you want structured resources, you should check out binance academy.