The technique is not tremendously important. This reduction tends to be large. Scanning for an image database is not likely to be anywhere near that. Image display for the end user is thus noticeably degraded. Additionally, even if this was no difficulty to the owner of an image database, the end-users would likely not have such powerful systems.
Compression helps, but many of the forms currently available are far from perfect.
A database of ten thousand of these images would require 2,500 megabytes. Using a better connection, such as direct ethernet access, would reduce base transmission rates to almost nothing, but decompression and incidentals would still have an appreciable effect - from request to actual viewing could still take from 30 seconds to a minute. The standard viewing screen for computer users has a resolution of only 72 dpi and measures less than 9 by 7 inches. That means that the scanned image used in the example above would overflow the screen extensively if viewed at its best resolution. In order to get the entire image onto the screen, it would have to be reduced, which requires discarding information.