And that's precisely why we need to keep all those TX's on the mainchain.
Why ? If we split same amount of transactions into 10,000 chains then
a) you can mine all 10,000 chains (it will cost you same resources as 1 BIG chain) -> big corporation
b) you can mine/verify only 1-3 small chains on your phone -> 99.9% ordinary people
i pointed out upthread how that will lead to tremendous centralization of mining as small miners with poor connectivity would be crushed trying to deal with 10000 chains at once in terms of resources, maintenance, coding reqs, etc.
not good.