Why are backbench mps important?

It decides the topic for debate on the floor of the Commons and in Westminster Hall for roughly 1 day per week.
MPs pitch ideas for debate to the committee, which takes account of backbench opinion and select committee reports when determining subjects for debate.
Topics selected for debates that subsequently shaped the parliamentary agenda include a referendum on the European Union and the release of documents on the 1989 Hillsborough disaster (both debated in 2011).
But the government can ignore motions passed in such debates, as they did with the motion to lower the voting age to 16.
In 2015, a Petitions Committee was created which took over the task of scheduling debates on petitions. Most of these are e-petitions which have reached 100,000 signatures. In 2018, the committee arranged debates on the proposed abolition of the House of Lords, changing the GCSE English literature exam from a closed book to an open-book assessment and banning the sale of animal fur in the UK.

A rise in the number of backbench rebellions against government measures, even if the average number of MPs involved in particular rebellions has declined. Political scientists Philip Cowley and Mark Stuart have calculated that coalition MPs rebelled in 35 per cent of divisions during the 2010-15 parliament: the equivalent figures for government rebellions under Labour.
in the 2005-10 parliament was 28 per cent. Note also that if a government is not certain of getting its business through, it may choose not to proceed rather than risk an actual defeat in the Commons. The coalition government’s dropping of its House of Lords reform bill after the second reading in 2013 is an example of this.

A device that, subject to the approval of the Speaker of the House, allows an MP to raise an important matter requiring an immediate answer from a government minister.
Speaker John Bercow allowed a total of 3547 urgent questions in 2009-13, while his predecessor, Michael Martin presided over only 1234 in a much longer period.
Work and Pensions Secretary Damian Green was summoned to answer an urgent question regarding a benefit paid to disabled people in 2017.
Urgent questions have become one of the most useful tools for backbenchers to hold the government to account over its Brexit policy.
In 2019 Conservative backbench MP John Baron questioned Chris Heaton-Harris, the parliamentary under-secretary of state for exiting the European Union, about government preparations for a no-deal Brexit – raised the concerns of many about the possibility of no deal and put pressure on the government to either pledge not to leave the EU without a deal or to have an effective plan in place.