it's not entirely accurate to say that there have been no microwave advertisements shown on TV in the 20th or 21st century. Microwaves have indeed been advertised on television during this period, but their frequency and prominence in advertisements might have varied based on several factors.
Product Maturity: Microwaves became popular household appliances in the 1980s and 1990s. During their initial surge in popularity, manufacturers invested more heavily in advertising to create awareness and promote sales. As a product matures and becomes more widely adopted, advertising might focus more on product improvements and special features rather than general brand awareness.
Shifting Advertising Trends: Advertising trends change over time. In recent years, there has been a shift in advertising strategies, with more emphasis on digital marketing, social media, and online platforms. Traditional TV advertising, while still relevant, may not be the primary focus for some brands.
Market Saturation: Microwaves have become a common household appliance in many parts of the world. With widespread adoption, companies might not feel the need to spend as much on TV advertising compared to when microwaves were first introduced.
Focused Targeting: Companies may have shifted their advertising focus to target specific demographics or channels that better align with their target audience's viewing habits and preferences.
Brand Awareness: By the 21st century, most people are already aware of microwaves and their basic functions. Therefore, advertising efforts might be directed more towards new product lines, advanced features, or differentiating from competitors.
Regional Differences: Advertising strategies can vary from region to region, and it's possible that microwave advertisements might be more prevalent in some areas compared to others.
Remember that advertising practices change with time and the marketing strategies of individual companies. It's also essential to consider that my knowledge is based on information available , and there might have been developments or shifts in advertising practices since then.