Granted but it surely is a matter of degree and extent and also how much people feel an entitlement that their residential area should be safeguarded at all costs to the exclusion of other uses.
In mainland Europe there is a greater emphasis on mixed use neighbourhoods and this is taken for granted. The planners have taken the view that whilst there may be some change to traffic and increased footfall, this would have minimal disruptive effect as there is effectively so little going on there already. I used to walk around there even at school rush hour times and always noticed how remarkably quiet it was. It was lovely however whether residents are permanently entitled to such loveliness is a moot point. The proposed use is surely one of the less obnoxious uses that could ever be proposed in such an environment. You could get someone wanting to open up a homeless hostel up there or a bed and breakfast; both legitimate reasons. Is a nursery therefore not better welcomed with open arms for that reason as to an extent its very existence might protect the area against a more challenging one.

Childcare is also a business yes but really only due to the lack of other supported options. There are a few childrens centres which also operate as a nursery offering subsidised places but they are few and far between.
There are so many demands on childcare settings these days that there are substantial fixed costs regardless of the size of the business so it makes economic and financial sense to expand and increase income. I see nothing wrong with making money this way and do not begrudge anyone a healthy profit providing standards of service are up to scratch. Sometimes you have to expand a business in order to stand still actually.

The fact that there is a demonstrated social need should also be taken into account. I met people at the weekend who said they were paying £80 a day for a child in North London compared to £55-£65 in Forest Hill. We personally could not afford that level and hence both of us could not afford to work which in the long run would open families to greater risk of unemployment and financial distress as it really is not ideal these days to have one parent permanently out of paid employment. Prices aren;t at that level in FH but they could be if demand greatly exceeds supply, which is the way it is going.