The link to the article below gives an analysis of some of the research carried out on this subject.
Only a relatively small number actually had Pernicious Anaemia. It suggests that if levels are very low especially if there are symptoms intra muscular administration replaces the levels more quickly and reliably to prevent further symptoms.
However, it suggests that 1% of an oral dose is absorbed by passive diffusion and for maintenance 1000-2000mcgs should therefore provide an adequate daily replacement. It suggests that if oral treatment is to be used blood B12 should be monitored closely to start with and then annually if and when levels are stabilised.
Since part of the rationale for using the less predictable oral treatment is time and cost saving for the doctor it is clear that the additional monitoring would totally invalidate that argument.
What I find "hard to swallow" is the fact that a pill could have saved the thousand or so hours with the nurse giving me the over 600 B12 monthly injections during the past 45 years, plus twice that amount in travelling time getting to and from the appointments all for the sake of an additional pill to add to my daily pile.
The only options given me back in 1972 were to eat raw liver three times a day or injections for life.
Oral can be effective but it doesn't seem to work for everyone - one study in Canada showed that a significant number of patients found it suited them better so in terms of allowing people options its good - but not if it is going to be forced on people and then complaints that it isn't working are going to be ignored.
If Intrinsic Factor is essential to process B12 through the stomach would it not be possible to include IF with the tablets, sub-linguals and sprays or can it not be synthesized?
I seem to remember in the early days of P.A. reading about a researcher who chewed, swallowed and regurgitated meat and fed it to "patients" who didn't have IF and their B12 levels rose.
I checked on Amazon and there is in fact a B12/Folate supplement that contains porcine Intrinsic Factor I have no idea if this is effective or not, but it seems likely someone would have picked up on it and advertised the fact widely if it was helpful.
The BNF has its view on intrinsic factor complexes:
Apart from dietary deficiency, all other causes of vitamin B12 deficiency are attributable to malabsorption. There is little place for the use of low-dose vitamin B12 orally and none for vitamin B12 intrinsic factor complexes given by mouth. Vitamin B12 in larger oral doses [unlicensed] may be effective.
Mind, that ends by stating the ridiculous situation in which the potential of high dose B12 cannot be fulfilled by licensed products despite even giving a slight nod to their possible effectiveness!
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Oral B12 passive absorption evidence please. 
How do Intramuscular Injections of B12 work?
B12 serum versus B12 active 
Chronic Fatigue Syndrome and Fibromyalgia treatment with B12 injections and oral folate
