Why almost all decoder zero selected output?
It is natural for TTL to use active low signaling. This is because of its polarity asymmetrical nature. Low output drivers are typically stronger than high output drivers. Also unlike CMOS, TTL input switching voltages are much close to 0V than Vcc. Furthemore, you ca directly tie logical input to 0V, but not to Vcc, you need a resistor there. This cause open-low outputs are much more common than open-high ones (I cannot remember single chip with them). While it is better in many cases driven wire correspond to active state (e. g. for Wired-OR and hot plug) it is better to have low state as active.

So it is natural when designing TTL circuits to have active-low signalling.

If you still want design active high circuits you should look toward CMOS (4000 series chips): 4028, 4514, 4555 are decoders with active-high outputs. Also there 'migrated' chips like 74HC4028 which are (TTL-compatible) copies of corresponding CMOS circuits.