I don't think it's the literal spending money on snacks that impresses people; it's more about the thought behind doing that.
For example I work in a company where the salary is pretty good, but they're also super stingy in general. No snacks, no socials, shitty laptop, etc. It betrays a lack of interest in making employees happy.
The absence of things like snacks is also an indication of how much the bean counters are in charge, because as you say it's probably good value for money in terms of morale, but as soon as the bean counters come in they see you spending £1k/month on snacks or coffee or whatever and that's an easy thing to cut.
Not only that, but if the company once had these things, and then took them away, it might be the wake-up call that snaps an otherwise satisfied employee out of his complacency and cause him to start looking around where the grass might be greener. Steve Blank wrote about this in [1]. Congratulations, you saved a couple of hundred dollars but caused three good employees to leave.
For example I work in a company where the salary is pretty good, but they're also super stingy in general. No snacks, no socials, shitty laptop, etc. It betrays a lack of interest in making employees happy.
The absence of things like snacks is also an indication of how much the bean counters are in charge, because as you say it's probably good value for money in terms of morale, but as soon as the bean counters come in they see you spending £1k/month on snacks or coffee or whatever and that's an easy thing to cut.