In cases where the automaker won't sell replacement parts, that is because they don't make the part, but third parties do, and the part can be acquired from one or more third parties. (Note: in the case of GM and BMW, the below are third party retailers, but they also sell OEM parts, which GM and BMW do not appear to sell direct online.)
No, they literally do not. Automakers will generally sell replacement parts for any vehicles they currently sell to anyone willing to pay for them.
In fact, they usually have dedicated sites just for buying replacement parts. https://www.toyota.com/owners/parts-service/parts https://parts.ford.com/en.html https://estore.honda.com/
In cases where the automaker won't sell replacement parts, that is because they don't make the part, but third parties do, and the part can be acquired from one or more third parties. (Note: in the case of GM and BMW, the below are third party retailers, but they also sell OEM parts, which GM and BMW do not appear to sell direct online.)
https://www.gmpartsdirect.com/ https://www.getbmwparts.com/bmw-replacement-parts