I think it more stems from the fact that it's on the disc that you paid for so to have that content locked and making you pay more money to use it is bullshit.
Old argument I know but so is the topic, it's like you buying a car that has fully functioning, handbrake, mirrors, whatever you want to use here but you have to pay extra to use them.
How about a house you buy a house but have to pay extra to use the bathroom....
See where it's going?
Just to note I'm ok paying for DLC if it's released a reasonable time in the future.
Again I liken it to my above examples.
If I buy a car everything that comes on the car I bought work from day 1 but if I want to upgrade it....say new wheels, etc I have to pay extra.
New house? I can use everything as soon as I buy it, if I want to upgrade it later...new cooker or whatever then I pay extra.
Conclusion when you buy something you should not have to pay extra to use a feature that is included in the product you bought, an upgrade or add on to that original product then fine.