Sounds good in isolation, but as others have mentioned, in some (most?) places, accepting money like that would be considered a professional activity, and you suddenly must worry about a host of other distracting things that take time, effort, and preoccupations: incorporating, tax filings, invoicing.

Or you could pay someone to manage it for you, but you're still suddenly involving yourself in stuff that you hadn't even had the interest or intention to do anyways.

In my European country, for example, having a regular source of revenue [1] requires registering with the government as an independent contractor, which costs a bit less than 400€/month. Then you will need to extend invoices, with the consequence of having to worry about VAT (consulting is a service? I guess so it incurs in VAT), make VAT tax filings each trimester, store invoices for several years in case they are requested.

One day you look back and think "but, but, I just wanted to spend a couple hours per week on small consulting requests!". As a consequence, people are greatly discouraged if it's not going to be a serious path to make serious money.

[1]: Yes, revenue, i.e. regardless of profit, and in theory also regardless of amount, albeit in practice they won't enforce it for measly revenues if they are roughly below 1000€/month.