Yes it IS annoying. I don't think I know anyone who doesn't get annoyed by it. Including the poor staff who have to do it, to meet targets for the store, so the fat cat manager can get his or her bonus at the end of the year. 
As someone mentioned earlier, WH Smith are one of the worst. I go in to buy a newspaper, and I get a nearly-out-of-date Terrys Chocolate Orange shoved in my face, on 'offer' for £2. 
It happens in many other stores too of course, and I have lost count of the amount of times I get offered a storecard. 'Oh but it gives you 5% off this transaction.' Wow big deal 50 pence off my ten pound top! Errr, no thanks.
A year or so ago, DH went to buy a £300 laptop from Currys/PC world, and the assistant said I will just take you to someone from our 'PC care and advice department.' We were both puzzled as he took us to the back of the store.
We waited for 5 minutes and got agitated as we just wanted to by the laptop. The assistant in question said 'he will be with you soon.'
Upshot was, this 'help and advice session' was about blinding you with bullshit, baffling you with bollocks, assuming because you're 'middle aged or older,' that you know fuck-all about computers, (we invented them you wet-behind-the-ear little shit!) getting fifty quid out of you to 'set up the laptop,' and bullying you into an extra guarantee that costs half the price of the laptop.
So we got up and walked towards the door. The assistant panicked and long story short, he just sent us to the tills to pay for laptop.
FFS, we can buy a pack of blank CDs or a camera without all the faff, why do they think we need this 'PC advice and help?' We have been using them since the 1980's. Fuck off. 