That is the point of the problem, sometimes we are not unwilling to allocate our income every monht in a large percentage amount, but with the economic situation that still has to divide on other things that ultimately make us as minimal as possible to allocate it. That is not something wrong either, because there should be no compulsion that makes us ignore other needs, because if we do that it is something that is not wise either.
The most important thing when we do this is consistency, for me it doesn't matter when the percentage is more flexible, especially when our financial situation is up and down.
30% is a fairly large allocation because for me it is a very aggressive step in investing. However, as JJG said, those who do not have large expenses for their living are certainly a better choice to save themselves in their investment plans. Well, if they are able to survive by allocating 30% for up to 3 years, of course the achievements in BTC ownership will be quite large.
Apart from that, all the dependencies and unexpected expenses in life can also affect the level of allocation in investing each month. However, every plan has to be thought out properly beforehand to prevent chaos in their investment journey. Well, in my opinion, most of them are probably only able to allocate 10% to 15% of their income to invest.