I've only participated in Meta just a teensy bit:
But I don't think any of those upvotes were reflected in my reputation. Do Meta questions affect reputation? If not, then why?
Your meta rep count is synced with your main-site reputation. Meta is supposed to be a sub-site for community members to discuss the workings of the site, or talk about community activities/plans.
Votes on meta aren't intended to reflect quality, but agreement or disagreement with the ideas presented, or support/lack thereof for having discussions.
Therefore, it wouldn't make sense to have a separate set of reputation, or to have meta activity affect your primary rep gain. When you're penalized for downvotes, such as when you downvote answers on the main site, it discourages downvoting except when the answer quality is poor enough. But on meta, we want the community to voice their opinion freely, without penalty, so the best policies and decision can be enacted.
While you can't earn rep on the meta, you can earn a separate set of badges!
From the help page for meta:
Voting is different on meta.
Like normal Stack Exchange sites, Meta allows members to vote on questions and answers. For most posts, votes reflect the perceived usefulness: well-written, well-reasoned, well-researched posts tend to get more attention and more upvotes. Highly-voted and frequently-linked posts may become part of the community-curated FAQ or codified as part of the site’s Help pages.
Unlike normal Stack Exchange sites, Meta invites the community to discuss, debate and propose changes to the way the community itself behaves, as well as how the software itself works. On posts tagged feature-request, voting indicates agreement or disagreement with the proposed change rather than just the quality or usefulness of the post itself.
If you have an account on Science Fiction & Fantasy Stack Exchange, you have an account on its meta site.
You do not need to create a separate account for meta; once you are logged in on Science Fiction & Fantasy Stack Exchange, you are also logged in and may post on its meta site.
Votes on meta do not affect your reputation; your meta reputation is the same as your reputation on Science Fiction & Fantasy Stack Exchange (synchronized hourly), though you earn separate badges. You must have 5 reputation to participate on meta.