I qualified my civil services exam in 1982 when there was no paper of essay in it. Later, the Commission felt its need sinceit helps in correct evaluation. In 1992, it was started again and it was for 200 marks, that means, out of total 2000 marks, 200 marks are for essay. The exam format was again changed in 2013, but, essay was continued. It wasn't only continued but was given more weightage. Now the total number of marks of all the papers is 1750, out of which 250 are given to the essay paper. If compared, the marks assigned for the essay paper have been increased from 200 to 250 when the total marks have been reduced to 1750 from previous 2000. The important part to think here is whether it is done all of a sudden or it is a planned strategy.
Nothing is changed suddenly, especially, academically. IAS examination is definitely not a bureaucratic matter, but academic as it is determined by not only different commissions, but, also the contribution of ideas by intellectuals of their time. Now the question which is raised here is why are essays given so much importance?