A visitors visa is given to visit the UK for a short time for visiting the family. It is not meant to stay in the UK for as long you possibly can. If visitors frequently visit the UK and stay in the UK every time, their intention are not consistent with the genuine visitor. That violates the original intention of getting the visitors visa.
Of course while we have personally no bias or opinion on this, in the eyes of the UKBA, such visitors are abusing the type of visitors visa they have got. If the person tries to stay in the UK for a longer time e.g 180 days per year, compared to their stay in their home country, they may get a shorter authorized stay at the port of entry and may be given a warning(in Louzhu’s case). The visitors may also be denied entry into the UK and be sent home right away. Moreover, once your current visa expires or is void, you may not get the visa the next time you apply.