Lots of people do continue to use normal furniture finishes and see the wood on pens in the same way as wood in furniture or other flat work finishes. But they are not. Pens are handled 100s of times more than fine furniture is, and that puts pens in a different category. IF a person takes care of the wood pen like they should, then it will work.
Yes, some use BLO as a part of their regimen in applying CA. BLO in some cases is used as a lubricant for applying CA, but not always necessary. It is used in some cases as a mild accelerant for CA and in some cases it is used to bring out or pop the grain. I think probably a slight majority of CA users do not use BLO that much. There are times when some oils, including BLO and tung oil will stain the wood in the wrong way. I used holly quite often and oils would give it an antique ivory look. Not good when you want "white". For blood wood, it would cause the dark red to have a slight burnt orange look. For those with dyed wood, the warm amber effect of the TO and BLO would change their tint.
Some people prefer the natural look of wood and that is fine. A few makers like the wood look so much that they will not make pen with CA finish. That is fine too.
But experience has shown time, and time again, that the vast majority of pen buyers will choose a shiny pen over a sheen or wood look pen about 10 to 1 or even 50 to 1 in different market areas. So, if one is making pens for sale, the question is, will we stick with our convictions of sheen/flat wood finish or shiny finish that sells 10 to 50 times better?
CA is a much better protector than TO or BLO. The problem with flat wood finishes being used on pens is that furniture and flat work (our term for non-turned wood projects) are used TOTALLY different than pens. I have written of this on many occasions. TO, BLO and other great oil and finishes (and waxes to) do super for fine expensive furniture and old antiques. But these wood objects are not handled or treated the same way a pen is used.
CA, lacquer, water based poly, liquid acrylic, and some others provide some great protection on wood pens that oils and waxes do not. Some of these are harder than others and last longer. Some reveal the wood better than others but that is a very subjective subject.
How many times a day will we pick up a pen and put it into a humid pocket or move it from outside cold or hot and humidity and dryness, and then move inside to a totally different environment. Sweaty palms in the summer and the humidity in the shirt pocket to a dry cool air conditioned room. Furniture does not go through that kind of change at all. Fine furniture is wiped and cleaned and waxed on a regular occasion, especially when people touch it or handle it regularly.
People don't clean their pens on a daily basis and wax them as often as fine furniture routinely is cleaned. This puts pens into a different category of wood use and abuse than fine furniture and it needs a different protection scheme. There are a few people that will treat a fine pen the same as a fine piece of furniture. These folks are to be commended, but most people will not.
IF you sell a wood pen with BLO only or TO only with a wax finish, in about a year or so, the pen will start showing dark grime build up. Some customers will blame the seller for not finishing it properly. This has happened. Customers need to be warned verbally and in written form how to care for an protect their pen, or the wood will darken from hand grime of sweaty hands and humid pockets. I am not talking about dripping wet sweat but normal hands that we often think are clean. Think about the kitchen and where kitchen cabinets show hand use from constantly opening and closing. And kitchen cabinets usually have a good protection of poly, but still the hand usage prints are there. And a pen will be handled even more so.
TO and BLO are fine, but one must recognize the constant need for cleaning and waxing on something that is handled 100's of times more than fine furniture and other wood projects.
I am not against TO or BLO, as TO is and has been my finish of choice for more than 30 years when the project would allow it. I know what you are asking and I love the TO protection and way that it brings out a beautiful piece of wood. But overall, fine furniture and most fine wood products are not handled and treated the same way that pens are.