To get back to OP's topic, he could also ask this question as well: "If you are a swing or a position trader with a persistent edge, are you a millionaire yet?"
Most traders are ambulance chasers, they follow squiggly lines but by the time they've reacted and arrived at the scene the patient is dead!
here's proof: https://www.sciencedirect.com/science/article/abs/pii/S1386418113000190 Day Trading for a Living? by Fernando Chague, Rodrigo De-Losso, Bruno Giovannetti :: SSRN
You can research volume analysis based daytrading strategy. I know many daytraders use this method. And I know it is a high probability and high profit method and many daytraders are successful at it. But I myself don't use it so i don't know the details. Also, if you ever heard prop firms? You can find a section on this forum named" prop firms". They generally offer funded account if you pass their challenges. Most challenges don't allow positions to be held overnight and they actually ask traders to make 100% in 30 days. I know quite a few daytraders on this forum passed challenges and got funded accounts.
Imagine that you have the perfect trading system. With this system you ALWAYS buy at the EXACT low and sell at the EXACT high (and vice versa for short position). The average yearly move of the British pound (GBP/USD) is 2000 pips. The average daily move is 100 pips. The long term trader will make 2000 pips a year with this perfect system (he buys/sells on January 2 and exits on December 31) . The day trader, on the other hand, will make 100 x 250 (days) = 25 000 pips that same year with that same perfect system, more than 12 times more money. This simple example should give you an idea of the profitability of day-trading systems (compared to long term trading), even at the intuitive level....