Not only could it affect the match day revenues. A reduction in attendances would cause the match day atmosphere to change. Atmosphere and social interaction is something that attracts supporters to come to matches. So does the habit of attending live matches.
I understand that Northampton Town, Exeter City, Morecambe, Accrington Stanley, Portsmouth and Sunderland all suffered their lowest league attendances of the season when matches were streamed on a recent Saturday.
Clubs need to increase the walk-up attendance from away club supporters visiting. Live streaming does not help to achieve that.
At the moment it is only certain weekends and matches being considered, but this proposal is seen by many as a beginning of something that could develop further. Last season it was only for an overseas’ audience. That has changed already.
Several years ago one chairman mentioned that when streaming began it would need clubs to lower ticket prices to encourage supporters to attend matches. This would be required to create the match day atmosphere needed for television to follow the sport. Empty terraces and empty seats will turn audiences off from watching matches on television and will ultimately reduce the income sourced from those media outlets.
A recent Supporters Direct article on the subject can be seen here https://supporters-direct.org/articles/another-nail-in-the-coffin-for-live-football