Today, the overwhelming majority of I2C devices are 3.3 V logic. but this wasn’t always the case. If you work with old tech or with I2C on VGA/DVI/HDMI ports, you will see 5 V I2C networks ...

In particular, I2C is such a powerful standard ... One party on the bus is the one always initiating all conversations (old: master, new: controller), and this role is basically always static; ...