The games have corrected it with Shadow Generations reminding us of the other Robotniks. And also Professor Victoria in later media. IDW comics yet to answer for this.
Shadow Generations took place before Sonic Forces. IDW doesn't have to touch it, unless SEGA mandates them too.
They don't have to reject business opportunity, just saying it be more "safer" if Sonic IDW continuity was it's own and not of the games.
Real businesses don't choose the "safest" way because there is an inherent trade-off between risk and reward, and multiple organizational factors influence decision-making.
Playing it completely safe can limit opportunities for growth and profitability
But Sally and the Freedom Fighters still built up a legacy for themselves thanks to Archie Sonic continuing off where SatAM left off.I don't think they would lose interest as long as it has a good story. Sonic X wasn't canon but it was still popular in it's own right.
The current movies aren't canon, but we still want more.
Sonic X and SatAM were aired in TVs, most of people watched them for free.
Sonic movies is only once a year, not much money spent.
Comics? You have to spend money regularly for those.