It's an inconvenience for a specific niche of users, but it's a niche Apple has catered to in the past.
While the average user may not have any need for a 10 gigabit connection, that capability was especially welcome for meeting the demands of video professionals that need those speeds for pulling uncompressed video files from network attached storage, as well as other professional users that may have 10 gigabit available in the office. The older Mac mini could also be configured with a 10 gigabit ethernet connection, but the new M1 mini only offers standard ethernet. The older 2018 mini supported up to three. A related limitation – which may be attributed to the reduced number of ports, the limitations of Apple Silicon, or perhaps both – the M1 Mac mini only supports two displays, and only one of those over Thunderbolt.
