tl:dr; version:
bitcoin has no central body that will fly on a plane to YOUR town to train YOUR vendor in your town... emphasis YOU need to help your vendor if YOU want them to accept bitcoin in YOUR town.

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wall of text version:

street vendors (tourist gift stalls, food carts, novelty merchandise stalls) accept whatever is most common to their customers.

in tourist area's they will accept multiple currencies EG euro stalls accepting american dollars
in smaller towns catering only to local population they only accept the local currency.

i know these small businesses dont have the volume power to beg credit card companies for convenient fee rates. but if the only method of payment a CUSTOMER has to offer the stall owner is a credit card. then thats what the stall owner has to accept.

in natural adoption without intervention/pressure, its less about trying to convince the market stall owner to accept a currency. its more about having the local population owning the currency and wanting to spend it. locally, to then help make the market stall owner realise he needs to accept it as a preferred method of payment via locals asking vendors if they accept currency X.

i know some will say its a chicken and egg. for instance. if local people cant find anywhere locally to buy things with crypto then local people wont get crypto to then ask vendors.
but the opposite can be said. if local vendors are not asked if they will accept crypto enough times by customers they wont see the point of accepting it,

this chicken and egg problem is what holds up natural un-intervened, unpressured adoption at the small local business level.
this issue circles clockwise and anticlockwise where by its needs to be educated how easy it is to set up a bitcoin address to watch for payments incoming. (very very easy 2 click process) and how cheap it is to set up a method to exchange the currency to local/native fiat(many options)

it requires educating vendors. not waiting for vendors to miraculously start using it.
bitcoin does not have some company/central lobby/education group to educate vendors. instead any and all people on this forum can do their part of speaking to vendors in their local area about accepting bitcoin

again bitcoin has no central body that will fly on a plane to YOUR town to train YOUR vendor in your town... emphasis YOU need to help your vendor if YOU want them to accept bitcoin in YOUR town.