The argument for Civil Service systems is that if people are granted job security and the expectation of a generous pension then they will accept a lower income and offer greater loyalty and discretion in return. They also were expected to accept the burden in a free society of voluntarily restricting their political activity. If there is any empirical evidence to support this position then I am unaware of it. 200 years ago the term Civil Servant was used for both the elected Members of Parliament and the nonmilitary appointed members, literally servants, of His Majesty's Government. The three civilian elements of the government, the elected, the appointed and the career promoted became distinct in America. In the UK, but not the US, most of the appointed are drawn from serving members of the elected.
Now we appear to be going full circle as the supposedly impartial employees of the government are selected in a process that is rife with favoritism, enriches them beyond the level that comparably skilled people gain in the private sector, and grants them extraordinary pensions and benefits. At the risk of repeating myself any expectation of loyalty, discretion or apolitical impartiality is completely derisory. At the same time the elected Masters of the government have also gone full circle by merging their identity and values with the civil staff that they had once separated from. Not only is there now a revolving door between elected and appointed positions that was rare in the past, with a great blurring also between the appointed and career ranks, there is as well a common indeed collegial association and interchange between the senior levels of regulatory agencies and the officers of regulated entities. Where the 19th to early 20th century saw the elements differentiated the more recent record is one of centripetal integration back into a common mass.
Elected politicians now get to enjoy generous pensions after short periods in office. This began in America with some embarrassment over the financial distress of Mary Lincoln. It has now reached the point where a Congressman or Senator is encouraged to extract as much money as possible from corporations and constituents, often with the lively expectation of future benefits and then retire precipitously and keep the windfall. In any other circumstance that would constitute fraud. The protection for the legislator, aside from their having written the laws to give themselves this loophole, is that in order to sue for the absconded money the donors would have to confess to their intent to bribe. There was a case in England in which a Highwayman attempted to sue his partner for not splitting the loot. He was hanged for his trouble and the doctrine of "Unclean Hands" was discovered.
Can anyone articulate an argument for granting a politician a pension? If there was none then the pressure for term limits would ease. There would be less pressure for hypocrisy in worrying about their future rewards from corporate interests, they could be assumed and discounted. Each proposed act could be honestly debated on its merits with the future benefits and costs considered and the possible benefit to the legislator accepted. This does not mean that I would suggest accepting the corruption of serving politicians, only that I would not worry about the compensation of the retired. Why not have politicians restricted to receiving no benefits except from their public salaries and disclosed assets placed in trust while in office? If they gained no other benefit from their office while they exercised it, and none from the public subsequently, would it be worse than the present system?