A couple more advantages for the power plant:

• The power plant doesn't have to move. You can attach all kinds of stuff to it to capture its emissions and do something with them other than discharge them into the atmosphere.

You are much more limited when it comes to doing that for a car engine. You have weight, volume, size, and power constraints on car attachments that you do not have on power plant attachments.

• You can build power plants far away from high population areas. This doesn't help with emissions like CO2 that are harmful no matter where they are emitted, but for various noxious emissions that harm people who breath them it matters.

Car engines emit their noxious emissions in the cities in the midst of large populations.