k p, plenty of algos utilize "key" levels unrelated to trend lines, horizontal support/resistance (previous swing highs/lows or range extremes) and previous day's close, high or low.
You may think price stopped and found a lot of buyers or sellers at a totally random level, when in fact it's a price level that served as "confirmation" of strength or weakness at some time in the past. That means the level is likely to be defended if price revisits that level.
I call these key levels "defense zones" because a battle may be waged there. These levels serve as extremely low risk entries because unlike the key levels everyone and their grandmother is watching, when these defense zones fail, you rarely get slippage.
These levels are especially powerful in stock index futures.