The lack of an Auction House has caused players like me to be forced to take up 3 trade guilds. This restricts the other guilds you can join by a large margin. Moreso, guilds being account bound means I can't wind up in 20 guilds.
The current system would "work" if I could join 15 trade guilds and 5 "other" activity guilds, but without a real auction house, all items are hidden behind the guild-wall. If you aren't a member of a guild with the item you need, you won't find it.
This restricts commerce to zone chat spamming:
1. There is a risk of being ignored by players you irritate with commerce.
2. Players ignore others during normal conversations to see more commerce.
(Ignore should be used to remove offensive players, not to maintain commerce-only function in zone chat)
3. It can take you a VERY long time to find your item traveling to different zones trying to do commerce.
4. Many players don't enjoy haggling and negotiating with other people. This is something that many people aren't good at, and those who aren't good at it know they aren't so they prefer not to do it. They would rather place a vendor and declare one not-for-negotiation price and that be it.
TLDR: Without auction houses, commerce sucks. 5 more guilds means you could have more trade guilds for better commerce. Maintains current system, only change is number of guilds. For those who only want 5 guilds, they may make that choice. This intrudes on nobody but gives everyone an option.
Within; Without.