Should manufacturers provide circuit schematics & parts list?

Consumers often use home audio gear for a long time—often longer than the lifespan of the company who made the gear. A lot of threads on the Forum are devoted to trying to repair audio gear and requests for circuit schematics. A lot of these requests are futile and go unfulfilled because the original audio gear manufacturer is no longer in business. 

Should manufacturers adopt the practice of providing circuit schematics and parts list as part of their products’ owner’s manuals? How about upon request from the original owner?

Obviously, some manufacturers might balk at this suggestion if their designs are patented or protected by some trade secret. But I suspect those who do would be a small number and is moot in any event for a defunct company.
I recently paid $15 for an original paper service manual/schematic for my 1980's Toshiba receiver just to find out voltage for the lights that had burned out. I could not find a PDF on line.

So yes, I wish all components came with service manuals/schematics.

They are fairly easy to find for cars and I have them for my vehicles.

The one for my tractor was over $100.

Some companies will not publish service manuals or schematics.

A infamous one, in audio, is Melos. It's a problem for Melos owners, as melos went as far to scrape the model numbers off some of the parts.

In the HT pro and consumer video projector world, no one publishes service manuals.
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It is not only the issue of protecting their design, but also of protecting their reputation.  Poorly done unqualified repairs will make percentage of the gear sound worse or fail again, making bad name for the company. 
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If I manufactured an amplifier I wouldn't provide a schematic. Don't want to get sued if you poke around and hurt yourself or start a fire.
Schematics should be provided by manufacturers. Service manuals that are well-written with good diagnostic info (voltages and waveforms at test points, etc... ) are essential in my opinion. 
I don't think liability is an issue. The auto manufacturers have all put their service manuals out there for free. If there isn't liability there then there surely won't be in a piece of audio equipment.
Liability is not an issue. Liability can be waived upon acceptance of the circuit schematics or upon consumer acknowledgement of no consumer serviceable parts in the product. 
Automobile tech information is not free in the majority of cases.  BMW TIS subscriptions are 2500.00 per year plus the cost of the hardware to utilise it.  Figure at least 10000.00 for that plus training.

Twenty years ago, the information available to properly repair a BMW was not available outside the dealer network.  Today, that is not the case.  

I don’t see an advantage for an audio manufacturer to expose proprietary information.  The volume of service repair isn’t there.  (Hopefully anyway.)
Fortunately I have been able to easily find all of the FSMs (factory service manuals) for my Nissans and Infinitis for free on the internet.

As mentioned, my tractor service manual was more expensive and combined with the illustrated parts list was close to $250 if I remember.

Service manuals and schematics for a lot of vintage Japanese audio components are pretty easy to find on the internet cheap or free.

I thought $15 for the one I got for my Toshiba was pricey but it was not a common unit. It was also original paper and quite detailed.
From the service manual for my new oscilloscope -

5 Replacing Assemblies
The service policy for XXXXX Series oscilloscopes is unit replacement, so there are
no instructions for replacing internal assemblies in this service guide.

6 Replaceable Parts
Because the service policy for XXXXX-Series oscilloscopes is unit replacement, no
replaceable parts are available for the XXXXX-Series oscilloscopes.

You'd probably get a lot of that.

I'd like to see the manuals and parts lists available for a reasonable fee. Especially for older pieces.
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