Why isn't variation in elevation across DEMs of different resolutions reflected in the profile graph?

[BeatriceO_Hara]

I have a DEM at various resolutions: 1m, 3m, 5m, 10m, and 30 meters.

In Spatial Analyst I have interpolated the same 1km line across the each of the DEMs, expecting to get variation in the graph output....especially with comparison to the 30m DEM.  As you can see, the graphs look identical.  However, when I have identified a single point along the line you can see that the elevations are different but the difference is not reflected in the graph.  Does anybody have any idea what is going wrong here?

Thank you