It's a good question but complicated answer,
Mostly additional weight and expense if you question honest management. (if you can find any)
They are a good proposition in certain applications, for an example where you have pilots flying somewhat standard tasks such as charter in flatlands, corporate/VIP where you're not landing anywhere very challenging but might land in a yard where someone just installed a SWER since last time you were there, and forgot to mention it etc
But: Many transmission conductors are too large to cut (18-29mm) steel reinforced (most small gage are aluminum) and we don't have the mass or speed for the cutter to work correctly.
Landing in moraines or toe-ins to steep terrain etc, the bottom cutter can be a real danger. (I swapped ships one time back in the early 90's and forgot it had the cutters installed and nearly flipped the 212 over when it caught on a rock sticking out of moraine debris). We then removed the bottom cutter blade, but our PMI (principle maintenance inspector) said the STC was all or nothing, so we pulled the system out...
Personally I don't like them for utility ops, where logic would suggest they're most needed. But I can see the merits for other types of work...
Naturally, if I'd survived a wire strike because of a WSPS I might feel differently...
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