They charge everyone.
Agents don't have agreement from all landlords to fix any work at any price. The landlord might let the agency deal with it, or they might choose to deal with it themselves. And if you've got a decent landlord, it won't matter if they're on holiday, they will call a...
Probably because agents charge you so much for everything - we're going to check your bank, that'll be £100. Oh, and you want a contract, well that's extra. Want a reference when you move on, that's extra. Want a key to actually get into the property, that's extra.
PS - look on gumtree