Welcome to the forum, MaryAnn and Teddy A!
The reason it is difficult (if not impossible) to re-create grocery store frosting at home is because the frosting in the grocery stores (Publix, WalMart, Albertsons, Safeway, etc.) is made in very large batches (buckets) from commercial ingredients. The frosting has a LOT of extra ingredients to make it smooth, shelf-stable, and perform as needed when a decorator must decorate a new cake every 5-10 minutes.
These commercially prepared, bulk frostings utilize ingredients that CANNOT be made at home. Here is an example of 35-40 pound buckets of bases used in commercial buttercreams available from a commercial supplier:
American consumers have grown up with "grocery store frosting". We like it. We like the cakes. Most don't give a hoot that they are made in batches of 1000 and frozen and shipped to the grocery stores and high-turnover bakeries. Personally, I don't see a thing wrong with it. (Scratch bakers, please don't beat me up....lol.)
Sure, there are a ton of ingredients with long names that you can't pronounce, but that is common in many items we purchase at the grocery store.
Homemade cake and homemade frosting DO taste different. There will always be some people (kids and adults) who want the "kind from the grocery store". There will also be a fair number that like the homemade version better.