You sounds as if Bitcoin investment is risk free and guaranteed to be successful and I also want you to understand that buying Bitcoin aggressively does not just depends on your discretionary income but rather your level of aggressiveness totally depends on how much of your discretionary income that you are willing to invest, that's means that you choose the percentage of your discretionary income to invest that you be comfortable with, some can choose 5%, 10% or 20 to 25% just as they want and willing to invest with.
I get your point, but the way you say it sound like investing in Bitcoin is all about how aggressive someone wants to be, It's not only about choosing the amount to invest, you also need to understand the risks involved Bitcoin as well. Bitcoin is not guaranteed to be successful, even though someone chooses to invest 5%, 10%, or 25% of their income, it doesn't mean you will succeed. The most important thing is how the person understands the market, and how to prepare they are when prices change.
However, some people may believe that since they have extra money, they should invest it all at once, and that's never a good idea. Investing should be based on knowledge, planning, and goals, but not just on how much money you have or how aggressive you want to be. you are right that people can choose how much they will invest based on what they are comfortable with, but they must understand and be ready for the risks too.