So often we hear complaints about poor staff training and this is possibly one where the staff have taken it to heart a little too zealously in some cases - intimate questions should not be asked in a crowded space but you should be offered a quiet area if needed.
It is important for some meds that you know of any side effects/contraindications etc - this can be irritating when you know you've had them before but the assistant doesn't know that.
I guess it's a case of damned if they do damned if they don't.
Guidelines here:
//Pharmacy medicines
Only pharmacies may sell these medicines and a pharmacist must make or supervise the sale.
You’ll be asked if you have any medical conditions or take any other medicines, to check that it’s safe for you to take the medicine. For example, some nasal decongestants can raise your blood pressure, so you’ll be asked if you have high blood pressure before being sold the medicine.
Some pharmacy medicines may only be sold if the pharmacist is satisfied that it is suitable and safe for you to take.//
Source
http://www.nhs.uk/chq/pages/1325.aspx?categoryid=73&subcategoryid=101