[imstillhere]

I think the reason is more historical than artificial market segmentation. Long ago, the development of Ethernet technologies was targeted to achieve an increase of a factor of 10 for each subsequent generation, i.e. 10m->100m->1g->10g. The need for 2.5Gbit and 5Gbit only came with 802.3ac Wave2 devices, where a Wave2 MIMO AP can saturate a 5G pipe after subtracting WIFI overhead.

Also, 2.5G/5G Ethernet actually did not start out as an IEEE specification, but was started as NBASE-T/MGBASE-T.

From what I remember, the 2.5G/5G/10G devices actually will negotiate to determine the maximum datarate that will work.