Bombing no effect on entrenchment

[RPKUPK]

I'm playing as Axis vs AI 1943. From southern Italy I'm bombing a British armored corps entrenched (two shovels) at the port of Messina. Since I have multiple bombers in the area I have been bombing this unit successfully (repeatedly, turn-to-turn) to dissuade against attack on the Italian mainland. I can easily reduce its strength by half which is noted when I put my cursor over the unit. However the "two shovel" entrenchment level never changes and that goes for other bombings elsewhere. No reduction in entrenchment level. The level of defensive entrenchment seems to play a key role in defensive power of the defending unit and lowering the attack odds (still "1-1" despite a German infantry 16-5, and Italian infantry 8-5 poised to attack the 4-9 British armored corps) for an attacker.
Why no decrease in entrenchment with significant bombing?
And another question, related, is why stop at entrenchment level two(?), say, an entrenched German unit in Cherbourg, Normandy, sitting there for years(!) with a maximum level of 2.
That should be a fortress city (with a higher level of entrenchment).

[AlvaroSousa]

Reduced entrenchment - That is an SC2 mechanic. Bombing doesn't reduce entrenchment. Air power isn't nearly as important on troops as many think it is. Artillery is of big importance though and there is a specialization that reduces entrenchment when attacking. Air power targets effectiveness and strength. if you are playing the current beta strength is only reduced on the 1st attack and effectiveness reduction has diminishing returns.

Entrenchment levels - This is a corps level game not division level. Generally it doesn't take long for troops to "dig in". This level game shouldn't even have entrenchment levels. It should he assumed. But I added it for flavor.

[RPKUPK]

Oh no! You're taking away my 'go to' ... my fun, my toys? My ... pizazz. Boo.

[AlvaroSousa]

There is way more fun pizzaz than you think there is. It's in the strategy.