AFAIK the ubiquitous Sky dishes that have been fitted since the launch of its digital service was designed mainly for aesthetics, the wider than tall design (along with perforations) being seen as less of an eyesore than the traditional offset dishes that are slightly taller than wide - also rumoured that a certain R. Murdoch wanted to reduce the size of dish required to receive the digital service compared to that for the analogue service**.
A side effect with this style of dish is that it has a narrower beamwidth to help reduce interference from nearby satellites - but it also means that a special Ku Band LNB is ideally needed with an oval feedhorn to match the dish face (as opposed to a circular feedhorn for general offset dishes). The design was intended to optimise the dishes for reception in the UK & Ireland with the restricted skew options built in to the LNB (required because of the oval feedhorn) as well as a smaller horizon angle offset than most general Ku Band offset dishes (20 degrees compared to usually between 24 to 26 degrees) - probably to compensate for the low-ish elevation angle in northern & western locations looking at 28.2 East.
Finally, by bundling their own unique style of dish for installation (along with specific approved receivers, a much more "proprietary" change compared to the analogue service), it pretty much advertised the service since anyone seeing such a dish erected on a property in public view made people assume that they had Sky Digital - not quite as big of an assumption these days given how long the service has now been running, and how quite a few households now use such dishes for Freesat or FTA reception from 28.2 East (or in a few cases, aimed at other satellite positions), but it was quite an effective tactic of essentially using their customers as a promotion tactic without spoiling the face of the dishes with company logos (which some Pay-TV providers in Continental Europe do) that would at some point go out of date.
Other oval shaped dishes similar to the Sky Digital design are often seen for satellite internet installations, or for offset Ku/Ka band dishes that are intended for multi-LNB reception over several close satellite positions - some examples include toroidal dishes like the Wavefinders, the Visiosat/Cahors Bisat dishes, and in North America the likes of the DirecTV KaKu dishes that are designed for reception across several satellite positions using a proprietary set of LNBs.
** Considering that the Sky Digital service launched using an FEC of 2/3 on DVB-S compared to most other European providers at the time that were 3/4 or higher, there's probably some truth to it - when Astra 2D went into service, the transponders used an FEC of 5/6, but the higher powered spot-beam helped to compensate for the higher SNR required. Coincidently, a Symbol Rate of 27500 and FEC 2/3 has the same net bitrate capacity as an SR of 22500 with FEC 5/6, as used for the Astra 2D (10.7 - 10.95 GHz) frequencies.
