At least if you are still in training or studying and have to pay for most of your living costs (rent, food, hobbies, etc.) yourself.
In such situations, you may have 50-100 euros left over at the end of the month for possible investments. With an average return of 6%, you will have earned just under 2,000 euros (savings rate of 50 euros over 3 years) to just under 7,000 euros (savings rate of 100 euros over 5 years) at the start of your real professional life.
Sure, that's better than nothing. But with your first full-time job, you will usually be able to increase your monthly income by 1,000 euros net or more. So if you resist the lifestyle creep for just a few months and instead put the EUR 1,000 into your portfolio every month during this time, you will have made up for the EUR 50-100 per month that you have painfully saved over the years in no time at all.
You can use the 50-100 euros instead to treat yourself to something, work less on the side or simply buy good wine more often instead of cheap spirits.
Of course, there are also reasons to start investing small amounts as a trainee or student. For example, to get a feel for real money on the stock market. Ultimately, this is your individual decision. The important thing is to know: It's definitely not too late to start investing with your first full-time job. You can invest the money in yourself or other nonsense during your training/studies with a clear conscience.
And finally, a reminder: we are operating in an absolute bubble here. Many people don't have 50-100 euros left over at the end of the month during their training/studies and have to see how they can somehow make ends meet.
[Since my wording has caused confusion for at least two people: I'm only talking about investing in volatile assets like stocks, ETFs or crypto. It's not about saving for a vacation or building up reserves for a nest egg. Of course, trainees and students should also have or build up a nest egg of a suitable amount (see https://getqu.in/SIPivs/).
