In the spring of 1945 even the most fanatical nazis knew the war was lost. German soldiers would rather surrender to allied forces due to how they’d be treated, comparatively. Given that Red Army forces were after retribution and would (generally) rape and kill their way through captured towns wouldn’t the Nazis have preferred for the allies to take Berlin? Roosevelt was even keen (?) for the Soviets to take Berlin at Yalta but couldn’t have the Nazis made it relatively easy for the Allied armies and allocated those forces to the west?
The Allied leadership chose not to try to take it. The Western Allies and the Soviets had already agreed Berlin would be inside the Soviet Zone after the war, and Eisenhower had decided to send US forces through the centre of Germany towards Leipzig, to break the last fighting power the Germans had and achieve peace faster. The Nazi leadership could not give the Americans something they didn't want and that did not fit with the strategic goal of military operations at the time, which was to break military resistance quickly by splitting Germany in two in the centre (see for example, Aaron Stephan Hamilton's Bloody Streets).
Some American generals , and some British, did want to try to take Berlin since it was defended to the West by relatively light forces in the closing weeks - most German forces were indeed in the East. But this was not the decision taken (though there were some plans drawn up for an airborne drop and last-minute rush to Berlin, they were not acted on). Instead, Allied forces stopped at the Elbe river even though they could have advanced further east (though whether they could have taken Berlin is another question).
The Western Allies also rejected German offers of a separate peace which would have left a Nazi regime in power, so that meant that the Nazi higher ups would have likely fought an American attempt to take the city, and orders to this effect were given. Though we don't know how the German officers or soldiers would have reacted if the attack had come from the west, since most did prefer Western occupation or captivity to the Soviets.
EDIT: it's important to keep in mind the Nazi leadership was not thinking about what was best for the population at the time or in the future. They wanted to preserve their power then and there if they could, and at any cost (see for example Lakowski in Das Deutsche Reich im 2. Weltkrieg, vol 10). They barely made any preparations in Berlin to protect or evacuate civilians before the battle. If not they were prepared for many thousands more of their own people to die - Hitler even said the German people did not deserve to survive since they had failed in the war (See for example Ian Kershaw, Hitler 1936-1945).