Almost everyone who does ice dance starts as a solo ice dancer. Very few people learn the pattern dances (compulsory dances) with their own partner. If they take an ice dance test, it's usually with their coach as their partner, or with an ice dancer who partners with them just for the test.
Some of the people now competing in solo ice dance may never have had a partner. But they have continued learning the dances as a solo skater because they enjoy ice dance.