Would it be easier to apply for a UK visa if there is a host family to sponsor for you in going there?
Having a "sponsor" for a visitor visa application helps in only these two cases:
The plans for your trip that you present in the applications say you will stay in someone's home rather than in commercial accommodation such as a hotel. In that case the ECO needs to see proof that the people you're going to stay with are cool with that plan (and, in the case of the UK, also that they won't get into trouble with their landlord or council for boarding guests).
Your economic circumstances make the ECO think: "This person cannot reasonably afford a vacation that's as expensive as what he has planned. Something's fishy -- he's probably intending to find work in the UK, which is not allowed." Then it can help some to explain that you're getting money for the trip from such-and-such people. The application must contain documents to prove that the sponsor can afford to pay for your trip, and a convincing explanation for why they'd want to pay for your trip. For this kind of sponsor it doesn't matter whether the sponsor is in the UK or outside it.
An applicant who doesn't need either of those two has much better chances than one who does need them (and provides them).
In particular, "sponsor" does not mean anything even remotely like this:
Hmm, someone whom we already trust says this is a nice person that we should give a visa. They're probably right -- one of our own people wouldn't recommend a bad person, would they?
It also doesn't mean anything like:
Whoops, since NN is a citizen they have a human right to be visited by their friends, so unless there are extra strong signs of wrongdoing we shouldn't refuse the application.
Maybe. Maybe not. The UK wants to be convinced that the visitor will leave again.
- If it is unclear how the visitor can afford the trip, there is the suspicion that he or she has taken on debt that will be repaid by working illegally in the UK. A sponsor helps to clarify how the visitor can afford the trip.
- If the visitor has few connections to his or her homeland and strong connections to the UK, there is the suspicion that the visitor wants to join family in the UK and overstay or "live there through successive visits." A sponsor hurts by underlining the ties to the UK.