Every swap pays a fee, split among the pool’s providers in proportion to their share. That income is the only compensation for supplying depth, and it is set against the exposure described in impermanent loss.
Whether it is enough determines whether providers stay — and therefore whether your exit exists.
The arithmetic providers are running
Fee income scales with turnover. The impermanent-loss exposure scales with how far price moves. So the ideal pool for a provider is high volume and low net directional movement — lots of two-way trading that ends where it began.
The worst is a strong one-way trend on modest volume: little fee income, maximum divergence. Which is precisely why depth tends to leave during exactly the trending conditions a trader most wants it.
Why this is a trader’s problem
Because it makes liquidity predictable in a useful way. A token with sustained two-way turnover has a genuine economic reason for providers to remain. One that has trended hard on thin volume does not, and its depth is living on borrowed time regardless of how healthy the current snapshot looks.
That is a forward-looking read a depth number cannot give you, and it is why the direction of depth is worth more than its level.
Fee tiers
Pools exist at different fee levels, and the same pair can have several. A higher tier compensates providers for a more volatile pair; a lower one suits stable pairs where divergence is minimal.
For a trader that means checking which pool you are routed through, since the fee is a direct cost and the tiers can differ several-fold on the same pair. It belongs in the round trip alongside impact and gas.
The summary
Fees are why depth exists. When the fee stops covering the exposure, depth leaves — not out of sentiment, but because the trade stopped paying.