Interesting. I've observed this in other cities throughout Europe too. I do think that film photography is experiencing a resurgence, perhaps akin to the one that's been going on around turntables and vinyl records for the past 15 years.
Being in my late thirties, I'm perhaps outside of the demographic responsible for this resurgence (mainly 20-somethings, based on what I, just like you, see in the street). However I started with film myself in the early 90s, then tried digital SLRs for a few years in the 00s, and now I'm back to film. I'd like to suggest a couple of reasons, amongst others, for this comeback.
Firstly, and I think somebody else in the thread touched on this, the internet is saturated with images and social media encourages users to compete for attention and for likes. I think the 'film aesthetics' (if such a thing exists) is being used by many millennials as a vehicle to allow their content to stand out. I have noticed many new film photography users choose to retain dust on their negatives, and choose not to fix light leaks in their film camera, and use the resulting imperfections as creative devices. Art? Incubator of future art? Hipster ethics? Maybe a bit of everything.
Secondly, and this resonates more deeply with me and I'm sure many people in this forum - digital photography is expensive but ultimately, for many people, not rewarding. It is tiresome, and distracting, how a lot of the focus around photography nowadays seems to be about gear, gear, gear. We need the highest number of megapixels, the latest and greatest f/1.4 medium tele with the greatest #bokeh, we need super expensive software to post produce the shots. Just take a look at websites like
www.dpreview.com/forums. Thousands of people foaming at the mouth if someone has an unfavourable opinion on their favourite sensor, editing tool, brand, or lens. At the same time, little, and often mediocre, actual photography. I mean, there are entire discussions around FPS and continuous shooting capabilities. People getting upset that camera X is only doing 5fps rather than 6. I mean are we talking about Lamborghini vs Aston Martin here? Is everybody taking pictures of hummingbirds in flight in Costa Rica?
But back to my second point above, I think many of these young film photography adopters find the simplicity and low (initial) cost of film photography refreshing. You can still find an Om2 with a Zuiko 50 f/1.8 in Oxfam for 50 quid. Boots will still process your negatives in 24hrs for £4 or so. Any 22yo with a little spare cash can get an Epson V500 up and running and get excellent scans. Youtube, reddit, blogs are overflowing with advice on Vuescan, overexposing Portra, cinestill anti-halation and stand development in Rodinal. I would suggest that the whole creative flow, especially to someone who's only known photography through the screen on their mobile phone, can be extremely rewarding.
I am aware this wave of interest means traditional used cameras are more expensive. I'd imagine the higher prices will hurt the camera hoarders and the older demographics of collectors the most (spot these people on flickr: the only photos they have in their feed are ensemble shots of their 15 slightly different models of Rolleiflex TLRs, taken with their Nikon D850
). I actually think it's great when these venerable mechanical wonders of a bygone era (I'm talking about the cameras here) are back in the streets taking photos. Also, obviously more film users who shoot+develop+scan = higher likelihood of film/chemistry/scanner producers to stay afloat.
So what's not to like! Welcome youngsters imho