Cable ads aren't the same across the country, and very soon won't be the same across the city. Addressable TV will bring personalized ads no matter what you're watching.

As to why you may see a bunch of ads for similar products all of a sudden, there are a couple causes. When a new company/product comes on the market, they may flood the airwaves with ads to get their name out there, or they may not be familiar with how buying and scheduling TV ads works and will cluster things together so it seems like a barrage instead of spread out over longer periods. Also, when new competition comes to the market, the current leaders get nervous and increase advertising to retain their customers and try to keep them from changing brands. Lastly, it's the phenomenon about noticing something which causes you to notice it even more (I.e. "there weren't as many of [my car] on the road before I started driving one.")