Why do the cabinet ministers need the backbencher's support?

In a parliamentary system, the cabinet is the executive branch of government, and is usually simply referred to as 'the government.' The leader of the political party that elects the most members of parliament in a general election usually becomes the prime minister. The prime minister then appoints several of his/her party members to the cabinet. Most cabinet ministers are also members of the House of Commons, although one or two are members of the Senate. A cabinet minister can be neither; however, this occurs but rarely. Those members of the prime minister's party who are not in the cabinet are usually referred to as 'government backbenchers.' It is a fundamental principle of parliamentary democracy that the government (i.e., the cabinet) must at all times have the 'confidence' (i.e., support of the majority of the members) of the House of Commons. If a government fails to win the majority on any vote in the House of Commons, it is said to have 'lost confidence.' Another way to describe this would be to say the government was 'defeated.' Usually this would result in another general election being called. If a party, in an election, elects more than half the members of the House of Commons, that party is said to have a 'majority' government. In this situation, having the support of a majority of the members of the House (i.e., having the 'confidence' of the House) is almost automatic, because the 'government backbenchers' will support the government. However, if a party elects the most members, but not a majority of members, it is said to be a 'minority' government. A minority government can easily 'lose confidence' and be 'defeated,' simply by being outvoted by the opposition parties (i.e., those parties that elected fewer members than the government party). Thus, a minority government could be 'defeated' on any one of the several votes taken in the House each week. Generally, however, one of the opposition parties will introduce a 'motion of non-confidence' when it truly wants to 'defeat' the government and have a general election. A government has occasionally lost a vote in the House simply because not enough of its members showed up for the vote. Such a circumstance is embarrassing to the government, which usually, after a day or two, introduces a motion to the effect that the motion that was lost was not considered to be a 'confidence' motion. If this motion passes, the government is not 'defeated' and things carry on as usual (at least until the next vote).