The arXiv preprint (v1, May 2026) synthesizes two decades of Hubble observations to argue that UV spectroscopy remains essential for measuring hydrodynamic escape rates in exoplanet atmospheres, a process absent from Solar System worlds yet central to explaining the radius gap and rocky-planet demographics. Drawing on Lyman-alpha and metal-line transit data from systems like HD 209458b and GJ 436b, the authors highlight HST's unique access to the 1216 Å line for outflow detection, noting that hydrodynamic escape shapes early atmospheric evolution and filters targets for the Habitable Worlds Observatory. This review, based on literature compilation rather than new observations, lacks a defined sample size and relies on heterogeneous archival datasets with varying signal-to-noise limitations; it correctly identifies that ground-based alternatives cannot replicate the UV window. Original coverage often reduces Hubble to image archives, missing its ongoing role in linking escape physics to biosignature retention. Related work in Nature Astronomy (2023) on GJ 1132b escape and the 2022 ApJ survey of 20 hot Jupiters confirms HST's mass-loss constraints but underscores calibration uncertainties at low signal levels. The preprint's forward-looking section on instrument modes for the 2030s bridges directly to HWO planning, revealing how escape measurements refine habitable-zone boundaries beyond mere detection statistics.