I don’t see how the independence of the events makes it 50%. What matters is that they are equally likely. I mean, you could watch someone rolling a dice (or “die”). The dice rolls are independent, but if we consider two possible outcomes, rolling a six and not rolling a six, the probabilities are not 50%.
Uh… there are really 6 possible outcomes to that die roll (assuming a 6-sided die instead of say…a 20 sider from a D&D collection). The roulette wheel in the OP has only two possible outcomes. Red or black. Not at all the same thing as the die roll.
There are only six outcomes if you are interested in all six. And you could even say that there are more than six (e.g. which direction does the dice end up facing). If you are only interested in whether you rolled a six, there are only two outcomes, yes or no. And obviouly the two probabilities are not equal.