I have Alcatel L100v one touch USB stick and it worked great before the update to Catalina and the 64bit.

Catalina does not support any 32-bit applications. If Alcatel is uncommited to providing 64-bit support software, then your USB stick is useless on Catalina.

Why is an App required for a USB stick?

Because it is an LTE Mobile Broadband radio, and needs support software/drivers to work.

AHA, thanks. :O