Many middle and working class Germans wanted unification of the states. But they had very different reasons.
For the middle classes, unification could bring:
The new working class that had emerged in the towns wanted:
The middle classes would have seen some of the workers aims as a threat to their economic status. Concessions to the workers would have potentially affected income.
Nationalists were also divided over the question of what territory should be included in a future united Germany. Some believed a united Germany should include Austria (Grossdeutschland). Others believed that Austria and its empire should not be included in a united Germany (Kleindeutschland).
Lack of trust and differing opinions meant that different groups of nationalists struggled to work together. The nationalists were unable to present a united front to their opponents.
The German princes had promised increased democracy after the defeat of Napoleon. But they were not held to these promises and none were met.
When the Frankfurt Parliament met in 1849, debate on the constitution, elections and the rights of individuals went on for a long time. This allowed the Austrian and Prussian rulers to regain control of their lands before the parliament could take decisive action.