That's missing the point. Third. Parties.
We have them for practically everything. End users can't figure it out, the manufacturer (say Microsoft) doesn't give two craps, so a third party (>90% of my career) involves solving those problems for users.
If things were open sourced, that'd make my job insanely easier in terms of man hours invested in any project.
I've literally had to spend >100 hours diagnosing that Dynamics CRM 2013's main data import tool has a bug that they refuse to fix. (Ever since it launched.) The import wizard refuses to actually load TIMESTAMPS (as well as some other columns) in even though it specifically supports setting that column. So when you do a data import, ALL of the user's data is out of order. That's completely unacceptable for any business to have their e-mails, notes, all have the same timestamp and no proper ordering. So "all" you have to do is first diagnose that this is the problem, then find this super obscure website where a guy made a fix except his code is half completed and full of errors, then install the entire CRM SDK stack. Learn how to write a C# plugin that exploits the CRM SDK. Write the corrected version of this guys code. Compile it. Use the CRM SDK toolkit to "attach" the plugin to your CRM. Figure out (no docs) what messages/events the plugin is supposed to actually trigger on with no error messages (while it takes >5-10 mins of user input every test to find out if it worked and then remove all the data again from the DB.)
If that was open source, that'd be a one line of code fix and I wouldn't have to play the "prod the black box" game of trying to figure out exactly where the failure point is. Hell, just adding a debugger would be insanely powerful. And that was just "one" story I have with "one" product that I support out of dozens if not hundreds.
So that's the thing. Regardless of whether a manufacturer open sources or not, people like me still have to fix the damn problem. Failure isn't an option. The checks have to go out. The lung machine has to keep blowing. And whether or not the business makes it easy or hard, doesn't enter the equation (except in terms of cost and man-hours). Nobody cares that you want to protect your IP. They care that their damn time clock doesn't work and they've got millions of dollars of product to ship while their employees stand outside of a locked automatic door.
So the real question is simply: Do you love, or hate, the people who support your software? Because we're still here, every day, slogging through insane problems by poking blindly in the dark. Closed source software breaks just as often as open source. The difference is, that the essential third-party (me) has to bill 10X as many hours to fix the problem. So if you're a business, it's in your best financial interest to demand open-source code whenever not prohibited (security constraints, HIPPA, whatever).
Closed-source is like buying a car and pretending it'll never break down, or that the manufacturer has the time, energy, and willpower to come down to your house and fix it. Some might go that far. The other 99% won't. And if there's a piece of software that has zero bugs, I haven't seen it in my lifetime.
So to bring this back to IoT. When a clients IP Camera goes down, they don't give a crap why. They need it back up. Yesterday. And they especially don't appreciate buying expensive hardware that ends up having security flaws... and worse... that is physically impossible to close. The clients aren't going to easily understand, "I paid $3,000 for it, and it works fine, but I should NEVER use it because it could be hacked?" That's like buying a car and a recall hits that says "the locks no longer work" and instead of fixing the locks, or allowing a third-party to fix the locks, everyone is just supposed to stop driving their car. You'd never see that in the real world, but somehow "software is magic" so it plays by different rules.