Toasters typically don't have a window to see how toasted your bread is for a few reasons:
Simplicity and cost-effectiveness: Toaster designs aim to be simple and affordable for mass production. Adding a window would require extra materials and manufacturing processes, increasing the cost of the toaster.
Even toasting: Toaster manufacturers engineer their products to provide even toasting on both sides of the bread. By using precise heating elements and timing mechanisms, they try to ensure consistent results without the need for visual inspection.
Safety concerns: A window in a toaster could potentially be a safety hazard. Toasters use high temperatures to toast bread, and a transparent window could expose users to the risk of burns or accidents if they touch the hot surface.
Cleanliness and maintenance: A window could accumulate crumbs and debris over time, making it difficult to clean and maintain. Keeping the toaster clean is essential for safety and performance.
User experience: A window might not provide much added value for most users. Toasting times vary depending on the type of bread, the desired level of toasting, and individual preferences. Many people are content with the preset options and are accustomed to gauging the toasting level based on sound or time.
That being said, there are some toaster models available in the market that come with a transparent window or have some form of visual indicator to help users check the toasting progress. However, these features are not widespread and are often seen in more specialized or high-end toaster models.