These are the relevant rules from the submission guidelines, especially Rule Two: Eligibility:
Paragraph 2 explains the physical characteristics of the film itself:
A. feature length (defined as over 40 minutes),
B. publicly exhibited by means of 35mm or 70mm film, or [...].
C. for paid admission in a commercial motion picture theater in Los
D. for a qualifying run of at least seven consecutive days,
E. advertised and exploited during their Los Angeles County qualifying
run customary to industry practice, and
F. within the Awards year deadlines specified in Rule Three.
Paragraph 3 explains the disqualifying rules:
Films that, in any version, receive their first public exhibition or
distribution in any manner other than as a theatrical motion picture
release will not be eligible for Academy Awards in any category. This
includes broadcast and cable television as well as home video and
Internet transmission. Motion pictures released in such
non-theatrical media on or after the first day of their Los Angeles
County qualifying run remain eligible. Also, ten minutes or ten
percent of the running time of a film, whichever is shorter, may be
shown in a nontheatrical medium prior to the film’s qualifying run.
Paragraph 4 explains the submission requirements:
Eligibility is contingent on the receipt by the Academy of the
following information on Official Screen Credits forms, available on
the Academy’s website, to be signed by the film’s producer or
distributor (unless waived by the Academy), which shall include:
Paragraph 5 concerns certifying the submitted film credits.
Paragraph 6 concerns disputed film credits.
Paragraph 7 concerns disqualification possibility concerning film alterations post-submission.
Paragraph 8 states all films are eligible except if the film is submitted for consideration in any subsequent rule.
Rule Thirteen concerns rules for films submitted for the Foreign Language Film Award. A primary rule there (Rule B) states that "Only one picture will be accepted from each country."
So the conclusion is easy to make. The glory is in the winning, not the fact that you are submitted. Films have the best chance of winning within groups of limiting criteria - Be the "big fish in a little pond."