With what money?
To have cash available to buy MORE stocks that implies you had that cash on the sideline. What percent of your bankroll and for how long? Eg say it was 10% of your roll you kept in cash for the last 5 years waiting for a crash to invest. Let's you had $100 5y ago and say the market has doubled in the past 5y (which it has approx). You invested only $90 and today it was worth $180 while holding $10 in cash waiting for a crash. The the market drops 8% and you finally put that 10$ to use and the market rebounds immediately after you buy! You now have $180 + $10*(1.08) which is about $191. If however, you just invested the full amount $100 5y ago, you'd end up with $200 in the scenario.
So, it's not as simple as saying I wait for a crash and I buy. To do it, you imply you are out of the market with cash holdings which is always losing money.