Why does ActiveRecord in Rails not support Multiple Table Inheritance?

Question

I was trying to implement a set of models I had put together on paper and ran into an issue where I thought the best way to go about it would be using a Multiple Table Inheritance setup. However, after google searching I found that ActiveRecord doesn't support MTI... even though there are plenty of articles showing how it can be done. This had me wondering if I was setting up my models correctly if it's not implemented. So my question is why doesn't Active Record have built in support for MTI? If you are curious to what my model setup was 'going' to look like I'll leave it below.

class Player < ActiveRecord::Base; end
class CollegePlayer < Player; end
class ProPlayer < Player; end

Where a Player can be either or both of CollegePlayer and ProPlayer. Or in another example...

class Person < ActiveRecord::Base; end
class User < Person; end
class Player < Person; end
class Coach < Person; end

Where a "Person" could be a User, former Player, and/or Coach.

Answer 1

Rails 6.1+ delegated type

Rails 6.1 added a "native" way to implement Multiple Table Inheritance via delegated type.

Please, see the corresponding PR for details.