It's all about money. Look at almost any brand and you'll see that as you go up in price you get more wattage, bigger/more speakers and usually
more features. Everything is about having an amp at every single price point so that a buyer can go into a store looking for a <name popular brand here> amp and find
something for their budget, even if it's a POS.
That's why the non-intuitive thing is to just buy something used that's
not an amp for beginners. Even my very first amp (a terrible Univox) was bought used. The trick is finding an amp that's currently out of vogue so it's selling for peanuts.
What I miss is the good old days when a beginner's amp had a 12" or 15" speaker. In the early 1980s I found a 1970s 20 watt/1-15" all-tube Traynor BassMate that was loud enough to use on gigs. Nobody makes amps like that any more and used prices for tube beginner's amps have gone through the roof.
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Oh yeah, I got it for $65 from some guy who was using it as a PA monitor

Those were the days!!! I sold it years later for $150 (with the original tubes!!!) but now I see people asking $400+ for them.