If a competitor figures out how to build a tractor that is as good as the ones from John Deere then they probably can compete with John Deere directly--as in, "on their terms" with a locked down tractor that makes them more margin--rather than bother to sell unlocked tractors. The same issue happens with cell phones: users want control over their phones, but they also want good phones with good screens and good cameras. There are, in fact, phones you can buy that give you complete control, but they are the companies that have shit products and so are trying to use this as a differentiator to draw in a new market. If you are able to compete with the iPhone--like Samsung can, but almost no other manufacturer can (sometimes Google manages to pull it off with first party phones, but very few people buy those, so they are clearly missing something)--then you build a device as equally locked down as the iPhone and compete with it "on Apple's terms" as there is a nearly bottomless well of money that you can extract from users if you are willing to screw them and
force them to participate in your closed ecosystem.
Essentially, you can't just look at the one product in isolation and think "this should exist from a competitor", as if anyone could easily make a company to go out and do it... you instead have to consider the ecosystem of companies and the numerous barriers to entry (such as patents and limited supply lines and the enormous R&D costs) and what the incentives in the market are, and it turns out that, if your product is one where the competition is already scarce--Apple + Samsung make up 80% of the mobile phone market, with the rest likely targeting people who don't have enough money to pay for high-end phones; there is a similar thing going on with tractors, with five companies controlling >70% of the market, and AFAIK mostly now selling locked down machines--you can't just expect to magically find a competitor pop up that is going to fill this particular interest. If you manage to circumnavigate all of the hurdles to build a phone that works as well as an Apple or a Samsung device, you are almost certainly going to join the oligopoly and lock your device down also, as the incentives are just too poor otherwise. The only fix for this is regulation and, to the extent to which regulation actually already exists here, legal precedent.