I generally agree with you. However, suppose there are good reasons behind the deletionist philosophy. What might they be? Some possibilities:
(1) Inclusion in Wikipedia is a statement in itself. It says, "This is notable." In the case of non-notable subjects, the statement is false, and so the problem is one of inaccuracy.
(2) Information on a non-notable topic is very difficult to check for accuracy, update, etc. Thus, the proliferation of non-notable topics would lead to lower overall quality.
(3) Pages on generally non-notable topics would tend to reflect the viewpoint of perhaps just one person who considers the topic important, or, similarly, one company. They would thus be prone to excessive POV stuff, advertising, etc.
In summary, every argument I can think of boils down to lack of notability -> poor quality.
And perhaps that does mean that there should be a notability standard on Wikipedia. On the other hand, I think it is clear that a large number of those people labeled "deletionist" have a notability standard that is significantly too high. (I also think it is very clear that HN is notable enough for inclusion; I'm rather baffled that anyone would think otherwise.)
Honestly, no, there are no good reasons behind the deletionist philosophy as currently embodied on Wikipedia.
The problem is that, although Wikipedia has policies for maintaining quality and relevance, they have fixated on something which is not a policy (notability, which is merely a guideline) and given it a status so far and above all other policies that it's hard to see as anything other than irrational extremism.
A good first step toward improving Wikipedia would be the utter abolition of the notability guideline, replacing it instead with the much more useful and relevant question of "does this article present information which can be verified by consulting reliable sources?" (see policies: WP:V, WP:RS) This maintains quality and relevance (since now the criterion is not "I've never heard of it/it doesn't have X results in Google/etc.", but is rather "no sources can be found to corroborate these claims"), and does away with the endless wanking over what is and isn't "notable enough" for Wikipedia.
I can prove who I am and have acres of relevant links and sources to the bits of software I have written and the sites I maintain.
Do I deserver a spot there? I doubt it.....
Notability guidelines were always important in my WP time. I would say 90% of the articles I cam across doing clean up tasks were just grime that cluttered the place up. There is no point having useless stuff there - it reduces what relevant stuff you can find!
I still just don't see what harm it does to have not-notable-enough-to-you, but reliably-sourced, verifiable information in Wikipedia. What is the problem that deleting solves in this case?
(of course, the flip side: I have, I'm told, for a while been hovering just near the bare minimum criteria to be "notable" enough for Wikipedia, and the thought of having to endure the endless stupidity that is having an article about one's self frightens me to no end)
(1) Inclusion in Wikipedia is a statement in itself. It says, "This is notable." In the case of non-notable subjects, the statement is false, and so the problem is one of inaccuracy.
(2) Information on a non-notable topic is very difficult to check for accuracy, update, etc. Thus, the proliferation of non-notable topics would lead to lower overall quality.
(3) Pages on generally non-notable topics would tend to reflect the viewpoint of perhaps just one person who considers the topic important, or, similarly, one company. They would thus be prone to excessive POV stuff, advertising, etc.
In summary, every argument I can think of boils down to lack of notability -> poor quality.
And perhaps that does mean that there should be a notability standard on Wikipedia. On the other hand, I think it is clear that a large number of those people labeled "deletionist" have a notability standard that is significantly too high. (I also think it is very clear that HN is notable enough for inclusion; I'm rather baffled that anyone would think otherwise.)