A large share of London homes are flats, and a large share of those are rented. Both facts point the same way: the parts of a building that television has traditionally depended on, the roof, the external walls and the communal aerial, are not yours to alter.
In practice that means a satellite dish usually needs the freeholder or the managing agent to agree, and on a listed building or in a conservation area it may not be permitted at all. A communal aerial, where one exists, delivers whatever it delivers, and a single resident cannot improve it alone. Tenants generally need the landlord to consent before anything is fixed to the outside of the property.
IPTV sidesteps that whole category of problem. It uses the broadband connection already coming into the flat, so there is nothing to mount, nothing to drill and nobody to ask. A tenant in a converted Victorian terrace and an owner in a new riverside block set it up the same way, in the same ten minutes.
This matters most at the point of moving. London has one of the shortest average tenancies in the country, and a television arrangement tied to a dish, an aerial socket or an engineer visit has to be arranged again at each address. A subscription tied to a login moves when you do: the same details work at the new flat the evening you arrive, provided there is a connection.