there's a guy that i'm mutuals with on other social media who's on the young side, like just out of college, and he's figuring out what he thinks about politics. he's pretty smart and hangs around cool marxist(-leninist) people, but he's definitely trying to figure out stuff on his own, which is really cool and he's critically engaging with stuff well.
however, it seems like he's seen a lot of patsocs and ACP members bring up weird corners of Marx's writing to try to justify their positions. the particular case he brought up recently was about an ACP guy on twitter using the productive vs unproductive labor distinction to call baristas (you know, people who make coffee for usually really low wages) enemies of the working class because they are unproductive labor. my friend was worried that this kind of weird nonsense argument was necessary for marxists in general. me and some other people explained that no, the ACP guys are picking weird bits of Marx to try to justify their reactionary bullshit and we actually mostly focus on class and not this other stuff. so like no harm done here, but it makes me wonder how often those kind of things go unchallenged in other people's experience.
I think in a marxist sense services are simply considered commodities: a product, though intangible, whose purpose for existing is to be bought and sold.
However, I think massage therapists and plumbers are productive because they create profit and thus accumulation of capital for their employer (or for themselves if they're self-employed).
We look at them from the POV of who hires their work, e.g. the client booking an appointment, but the rendering of services is what matters and what creates profit: a massage company charging 100$ for a massage and paying their therapist 60$ per massage makes a 40$ profit off every client, rendered possible by the therapist's labor.
The bakery in your example requires both types of labor: the bakers are productive because they imbue value in a commodity, but the cashiers are not because they don't directly create profit, they turn the value of the commodity into its money-form -- from what I understand of Cockshott's video "Are barristas productive?". If the bakers are also the cashiers as is often the case in this late-stage capitalism period, they perform both types of labor: some of it is productive, some of is unproductive.
We can take another example: a capitalist hiring a chef. In either cases, the chef produces a cooked meal with his labor-power. If the capitalist hires the chef to cook a meal for himself (and provided the chef didn't come through a temp agency or whatever else but was directly hired as they used to do back in Marx's days), then the labor was unproductive: it didn't generate more capital. If however the capitalist hires the chef for his restaurant, the labor is the exact same, but it becomes productive because the meal is sold for a profit.
You know what? I honestly don't know as much as I'd like about productive/unproductive labour as it applies to industries in general, and services in particular. So instead of coming up with some kind of half-baked answer I'll go and read about it.
I recommend Cockshott's video! He's a terf but he's a very good economist