A. The likely reason for this is price increase of dram chips which resulted in ssd & ram prices increasing. Once the prices go back to their original levels this trend should also reverse.The new norms of 2020 laptop with U series processor be it Intel or AMD with their current generation offering
(A) U Processor = Fixed RAM = Dual Channel Configuration in most cases, Gone are days with Two RAM slots with One occupied.
(B) It is best for consumer if we get 4000U series processor with 8GB fixed and one slot remain empty, but laptop manufacture decided not to give that unless you like to spend more and opt for H or HS series processor.
(C) Right now All laptop manufacturer dumping 8GB U series processor in India as the cost cutting measure.
(D) IMHO they got the idea if Apple Macbook line up comes with 8GB Fixed RAM as base and Consumer of India paying the premium of buying those why not us ? Because the Macbook are Appliances which maintained by the Apple with closed eco system and there file system completely different. These are Normal Computer for Normal People.
Anyhow anyone wants a 4000 U Series machine with 16GB RAM (which is minimum for future proofing), they need to wait.
B. Even more important reason than this is the presence of IPS screen in all H/HS series processors even in their lowest end models compared to U version counterparts where IPS screen is rare. For reference, HP 60k laptop with ryzen 3700u still comes without ips screen.