Why is there a daily inequality for low tides? I understand why there is a daily inequality for high tides. What I do not understand is why the low tides are not equal. The data all seems to be somewhere along the lines of but the theory seems to point to
That is, a greater daily inequality for high tide and none for low tide. I know that there are things to consider besides the moons influence, but the data pretty clearly rises above the noise in its consistency.
The water for high tides needs to come from somewhere; the mean sea level should stay approximately constant, as long as wind is neglected. That way tides are a kind of oscillations.

In the first of the two diagrams a low low tide is followed by a high high tide, and a high low tide is followed by a low high tide. That way the mean sea level, averaged over one low tide - high tide period remains constant:



In the second diagram you need to average over two low tide - high tide periods to get a constant mean:



The first diagram can be explained by the superposition of semi-diurnal tides, while
the second diagram needs an additional diurnal constituent. Depending on the amplitude and phase shift of the diurnal constituent relative to the semi-diurnal constituent we can get different resulting oscillations.

More about tides and their constituents.