Any electoral system, including the FPTP electoral system, has advantages and disadvantages.
Advantages of FPTP
Close MP-constituency relationship: One person is elected for each constituency and this usually means there will be a strong constituency-MP relationship. It also means that if voters do not like their MP they can also vote to get rid of an individual person.
One party strong government: Usually one party wins the election which means the winning party gets five years to put its plans (given in its manifesto) into action.
Simplicity: The FPTP system is easily understood and familiar. Voters were given the chance a few years ago to get rid of FPTP for UK parliament elections but they choose to keep it.
Disadvantages of FPTP
Minority of the vote: In most constituencies more people (in total) vote against the winning candidate than for them. Sometimes an MP can be elected on a vote as low as only 35% of the vote.
Less than 50%: The winning party is also usually elected by less than half (50%) of the voters. More voters usually vote against the winning party than for the winning party. In 2015, the Conservative Party won the election and formed the government but only 36.9% of the people who voted chose to support the Conservatives. The other 63.1% voted for other parties.
Tactical voting: FPTP encourages tactical voting or people not bothering to vote as they think their vote will have little chance of helping elect their candidate.