I wouldn't say most electronics are designed to not be repaired, it's more of the result of the process.
SMT (surface mount techonology) and lithography for semiconductors are major contributors. It's far cheaper, easier, and produces less waste than previous manufacturing processes.
Companies really don't want to make anything open source but they'll love using open source technology to design their products. They'll also try and prevent people from repairing their products by simply stating "propriety knowledge".
People should be lobbying hard for "right to repair" in the US and forcing companies to produce products that make repairing items easier/cheaper. If companies were forced to open source their products consumers wouldn't be paying 2,000 dollars to repair their ECU/PCM on their vehicle.