People wearing their Sunday best was something I noticed, too. There is a paper written about this movie that someone linked to on my blog. In this paper, the following is recounted, which may perhaps explain their clothes:

Harbeck intended to film the downtown area of the city from a hand-cranked camera
placed at the front of a B.C. Electric Railway streetcar and to film from an automobile while
traveling through the city’s famous Stanley Park. The following morning, the Vancouver News
Advertiser conveyed a request from the filmmaker: “Mr. Harbeck would feel obliged if the
stores en route would furl their awnings.” The newspaper also alerted local residents to the
opportunity to appear in the film: “Anyone who wishes to be taken in the picture should stand
out in the streets as the car approaches or cross in front of it.”
The event evidently attracted great interest. On 8 May 1907, the Vancouver Province
reported that “many prominent citizens were suddenly stricken with kinetoscopitis yesterday”
and reassured readers that “kinetoscopitis is not nearly as serious in its effects as spinal
meningitis.” The article observed that “the way that prominent citizens suddenly discovered
that they had business on the other side of the street and strolled across sort of unconcerned
like, when they saw the kinetoscope coming was very amusing to those on the front of the car.”
The detailed account also explained how the filming had been timed in order to catch crowds
returning home for lunch, and described the route through the downtown core (along streets
that still exist) and along two residential streets in the city’s west end. There is no indication
that any filming was actually done in Stanley Park as planned.

So, it seems like some people would have wanted to get a little slice of immortality by appearing in this film and they may have tried to look their best while doing it.

ahh, yes kinetoscopitis. whenever ben afleck is in town, i as well have this sudden urge to put on a suit and walk across the street!
funny how after all these years, people are still crossing hastings with no regard to their lives. however, now the infliction is called “iamtoodrugouttocareits”