Trouble is that successive governments (of BOTH colours) made pensions into that by forever changing the rules and actively bringing in changes/exemptions that made pensions into a "savings scheme" as an option for IHT planning.
It's not the people using it as such who are the problem, it's the incompetent/incoherent politicians who've embraced "tax planning" into legislation for a few decades.
Look at Brown - he changed the pension rules, he brought in tax-free ISA, he reduced basic rate income tax, etc etc. He, too, was a tax saving Chancellor.
Both colours of politician have brought in all kinds of tax incentives such as venture capital trusts, enterprise investment schemes, bonded warehouses, enterprise parks, Freeports, film partnership tax relief, etc. They've actively brought in new IHT and CGT exemptions and reliefs. All of these "drive" behaviour.
So you really can't blame people for using pensions as a IHT planning tool, as the politicians have expressly brought in exemptions and reliefs for them to do just that!
Most tax planning isn't using "loopholes", it's using schemes specifically brought in by politicians to encourage certain behaviours. Of course, those same politicians cry foul when these schemes are used in a way they didn't expect, but they've only themselves to blame for that!!