Two short lines carry a quiet complaint. The speaker notices that plenty of people fall in love, but few of them go deep enough to remain there. The poem plays on the common phrase "falling in love": falling is easy, almost accidental, but staying takes something more. The image of depth suggests that lasting love needs commitment, patience, and a willingness to go past the exciting first stage.
The speaker sounds disappointed, maybe a little weary, as if they have watched this happen again and again, or been on the receiving end of it. There is no anger, though. The tone is calm and matter-of-fact, which makes the observation sting more. The mood is wistful and reflective. The brevity helps: the poem simply states what it sees and stops, leaving the reader to think about whether love is something we drop into or something we have to keep choosing.