1080p 15fps streaming

I understand using 1080p 30fps uses twice the bandwidth of 720p 30fps but why not make a option to stream 1080p 15fps, I mean it is the same bandwidth and sometimes when I screen share small text the 720p isn't enough to read it, so I don't understand why you guys don't make 1080p 15fps a option while it uses the same amount on bandwidth as 720p 30fps