The number is real. The explanation usually is not.
Broker disclosure documents required by European and UK regulators consistently show that 70–80% of retail CFD accounts lose money. The figure is published on the brokers' own websites; you can check your own broker's.
The usual explanations are wrong, and being wrong about the cause means fixing the wrong thing.
What does not explain it
"They don't have a good strategy." Most losing traders have several. The internet is saturated with strategies that work well enough. If strategy were the constraint, buying a better one would fix it — and it demonstrably does not.
"The market is rigged." Retail order flow in major FX is a rounding error against interbank volume. Nobody is watching your 0.05 lot. This explanation is popular because it is comfortable, and comfortable explanations do not change behaviour.
"They lack discipline." Closer, but it is a label rather than a cause. It says *what* happens, not *why*.