Quote from CTTrader:
An old adage: "You can't bank a %, you can only put $ in the bank."
In longer term trading or investing % return is a useful benchmark, especially if your goal is capital appreciation rather than income. As the time frame shortens and the goal is current income % return becomes less relevant.
For example in day trading % return is almost irrelevant because meaningful results are limited by the ability to use all of your capital. Trading a $100k account, even using 4x leverage, you can still only trade 8,000 shares of a $50 stock at a time. To make 1% ($1,000) you only need to take about 15 cents out of the market to make this after fees. Even with lower priced stocks and somewhat larger accounts you can still trade. The point is that you can get orders filled and not move the market, assuming you are trading stocks that have good volume.
As the account grows this becomes impossible. At $1 million account size you now need $10k to make 1%, but the factors limiting your ability to trade haven't changed. In the example above if you take the same 15 cents out of the market you need to move over 66,000 shares. Not as easy as moving 8,000. What that means is that you can only utilize part of your capital to generate 1% on the total amount. The rest just sits there.
I know the example is simplified , but the purpose is to illustrate that at some point you simply can not get in and out of the market to generate 1%. But you can still make $1,000 per day ($250,000/year) and put the excess capital in another investment.