A4 had some of the standard items (Hugo awards, masquerade, etc), but failed to have some of the others (con suite, dead dog party, etc). Some of this makes economic sense. A con suite (i.e. place while provides softdrink and nibbles all day for free) would indeed be very expensive, given how our hotels behave. Some of it makes no economic sense at all. Having rooms paid for and not using them is quite inane. A dead dog party would have cost very little. (Though, as I guessed by the announcement of the volunteers' party at the closing, that and the hallway outside pretty much turned into a de facto dead dog anyhow.)
As you've mentioned, some of the problem is fear. How much divergence from the norm would cause the powers that be to try to sweep in and kill it? Who knows? A4 would have been much better off a month later in decent weather. Some few SMoFs would have been annoyed if A4 wasn't on their chosen US-centric date. Would they have cared enough to try to, say, run an opposing bid? I doubt it. But then, I'd let them if they were that obsessed. My preference is "do it well" in front of "do it here". The egos running A4 would (understandably, even though I don't agree) have those preferences the other way around, and hence buckled to most demands for keeping to the US McWorldcon standard.
When you ask whether it's fear of change, you have to be more specific. If change means taking away, altering or moving something, yes. Generally, fans will object to the things they want and expect being taken away. (It was obvious that lack of a dead dog pissed a lot of people off and soured the end of A4.) They won't object to new things being added.
Does fun evening entertainment ever happen at Worldcons? You bet. At Montreal last year, the convention centre opened up their rooftop area for us on the night of the international fireworks display a few blocks away. Sure, the con wasn't providing anything beyond rooftop space, but they could have just ignored it too. The 2004 Worldcon
had a brilliant first night evening programme
. It was possibly the best start to a Worldcon ever. If anyone feeds you the bullshit about Worldcons never having evening programming apart from the Hugos and masquerade, point them at that. It's just a cop-out.