To quote some World Bank slides:
Pension Reform Policy Options:
- Increase payroll tax base or rate
- Add additional earmarked revenues or general taxes
- Reduce benefits (e.g., change indexation)
- Reduce eligibility (e.g., raise standard retirement age)
- Restructuring, e.g.:
- Add (or substitute) defined contribution tiers
- Add automatic balancing mechanisms (NDC)
- Add “boundary straddling” automatic stabilizing mechanisms
...usually tried in roughly that order
Generally speaking people on the center-right don't like to pile up more/higher taxes/contributions. And also generally speaking, people don't like their benefits cut, but that did happen e.g. in Greece, simply because cutting pensions in half has no real substitute in terms of raising the retirement age.
As for the last part (3), it's complicated to add multiple layers of contributions etc. Generally speaking it's the poor[er] who pay more of their income towards pensions anyways. And in NDC [Wikipedia]
Unlike in PAYG pension system, there is no guarantee that the worker can expect decent pension in his retirement, since it is based solely on his contributions and the notional rate of return.
Anyway, going back to the World Bank slides, there's this arguing against the more complicated schemes:
Stealth mechanisms for loss imposing pension reforms [suffer from lack of]
Clarity--if workers are to adapt successfully to new
pension policies, they must be given clear signals early
about changing their savings and retirement behavior.
While France is largely a PAYG country, its system is already using various tiers etc. Yeah, they could tweak those and make just some people worse off. But what happened when some people in France thought they were unfairly targeted by diesel fuel taxes? [A: Years of protests.]
My question here is why the arguments are: raise the retirement age or not, nothing else.
That seems to be the most contentious issue, and traditionally has been so, see e.g. 2010 protests, but it's hardly the only measure that was considered/included, although I only found this bit in English from January, so I don't know how much of it made it to the final law:
"Another key measure that the government is counting on to get the reform accepted is the increase of the minimum pension for low-income workers who have a full career to 85% of the net minimum wage, i.e. nearly €1,200 at present. A measure extended to current pensioners. "Nearly two million small pensions will be increased," said Elisabeth Borne." [...]
"More than ten years after the abolition of the gradual cessation of activity, the government announced the return of a system of gradual retirement in the civil service, "on the same principles as the existing system for employees and the self-employed," according to a government press kit. We will allow civil servants "to go part-time two years before the retirement age", i.e. from the age of 62, said Ms. Borne."