Not only does it help with hearing, but with sight as well. Two eyes looking horizontally at an object produce a dataset for the brain to process, but the depth perception is constrained to working in the horizontal plane. Tilting the head expands this into the third dimension, providing a lot more for the brain to work with.
For singular dots in space your argument would be valid, but real objects are often more complicated. If the eyes can’t reliably lock onto the same spot along the X-axis due to a repeating pattern or a complete lack of detail along said axis, tilting the head shifts the whole situation and allows the eyes to zero in on a fixed point to perceive depth. An extreme example: If you look at two horizontal featureless lines (offering no details along their length to lock onto, brushed metal railings for example) positioned one behind the other, running perpendicular to the field of view in the direction of the X-axis. The only way for depth perception to work here is to tilt the head to introduce a difference along the Y-axis. Repeating patterns with the right spacing (e.g. grids, lattices) in that same plane can also confuse depth perception, in which case the head tilt often helps.
Another (marginal) benefit of head tilting is the fact that as the head rotates, the eyes physically move, possibly revealing additional detail that may have been obstructed from the previous vantage points. All this for a much lower energy expenditure than the whole animal moving itself.
Oh and one thing that popped into mind from personal experience as I am writing this: In darkness tilting the head helps discern between shapes that are just lingering on your retinas after looking at a brighter thing earlier (rotates along with the eyes) vs. dim things that might actually be there right now (stays in the same orientation relative to the surroundings).