What what exactly if I may ask?
Let me quote it again for you.
Obviously, it can be done by "reinvesting" everything we earned at previous rolls without changing any other setting (like odds, initial bet amount, increase, etc)
See the bolded highlighted parts? Reinvesting, Without changing, Initial Bet amount? I'm just wondering how you could reinvest without changing the initial bet amount? Let's say you have won a lot and you have a profit with it. How is it not changing the initial bet amount? I think it's better to start with a smaller initial bet after winning a lot of rounds using Martingale
The word was double-quoted to avoid possible misunderstanding and confusion. Anyway, if that gives you peace of mind, substitute reinvesting with increasing your balance
How can it make practical sense if you never have unlimited funds in real life?
That's the sad truth about it, that's why it's never going to be that profitable and not the go-to strategy for everyone who is gambling
It is not only that
All legit casinos have an upper limit on how much you can bet, and many of them have a lower limit as well (which is different from the lowest denomination of the coin gambled). That basically puts an impenetrable barrier, a roadblock of sorts, as to how much you can earn (or lose, for that matter) even if you had a drainless fountain of wealth. Apart from that, your bets are also temporally limited, i.e. you can't make more bets per unit of time as preset by the casino
All that, taken together, severely limits how much you can earn even using the most riskless martingale settings. For example, when you are using doges, which allow you to withstand very long losing streaks practically impossible in real life, you don't need to have insane amounts of money to take advantage of that, but your earnings, while kind of guaranteed, will still be dust anyway. On the other hand, if you just like seeing your balance grow, that's pretty much it