Discretionary income is not meant to be spent on things that are not meaningful; it is the money left over that needs to be spent wisely. As a reasonable investor, it doesn't make sense to go clubbing when you can't afford it, and there are other tasks that are valuable to meet. Generally, money is meant to be spent, but if you spend it on things that have no meaning and no value, then you will fall back to square one. With discretionary income, you need to comport yourself very well and know how much you need to invest in Bitcoin and what will be left with you.
As an investor, it is very important to have knowledge of money management, to know what you want, how much should be spent, and the amount of money that needs to go for investment. If you pursue a lifestyle that you cannot afford, you may end up being unable to make any investments.
I think you’re not getting the whole idea of discretionary income, despite that we keep saying invest your discretionary money it doesn’t necessarily mean you MUST invest it, or it’s only for investment. Just like the name, it’s money spent at the discretion of the owner. He can choose to spend it on whatever he chooses as he sees fit.
We can only advise or suggest the individual uses it to invest in bitcoin or any business that will be profitable to better his future instead of buying or spending on what’s not actually needed (like you said not meaningful).
You should know it’s with your discretionary money you satisfy your wants.