For me it's the cost, but DD15 is very keen to be a paramedic so her maths needs to be top notch.
Her old school were positively useless, constant supply teachers that couldn't consistently teach the curriculum (not their fault at all) with no sign of a permanent teacher coming in. This wasn't just in maths but other subjects too, and it was the catalyst for her moving.
She is now much happier in her school, getting consistent and good results, but because of the poor organisation of her old school, DD struggled with maths lessons.
I'm utterly hopeless at maths (I get very confused and frustrated once something goes into multiple figures, find it hard to "read" if that makes sense, have never been mathematically minded, and use a lot of number aids like calculators and Excel to complete day to day financial tasks because I just can't do it) so there's no way I could have got her up to scratch.
So, to the tune of £25 per hour, she's having weekly lessons right up to her GCSEs. She needs to take the higher paper, and her tutor is very confident that she will be able to do this.
Pricey yes, but it will be money well spent if she gets the results she needs. Tutor is also a very friendly guy, who is pushing her just hard enough. DD is very pleased with results so far as am I.