...an imbalanced partner because the highs and lows, and push and pull dynamic is stimulating. Despite feeling exhausted and depleted from the relationship, the dopamine rush they feel during the high period is exhilarating. It is also validating whatever anxiety they felt during the low period.
Unfortunately, having been in a string of this type of relationship will alter the person's perception of what real, and healthy love should look and feel like. Healthy love doesn't feel real or stable to them. Chaos and drama is more familiar. Because they've developed a habit of inciting chaos, drama, insecurity, and anxiety in their former partner(s), they will start to exhibit behaviors that trigger those responses in a healthy partner after the honeymoon phase. This is to get the same reactions in order for them to get the same dopamine rush. If the healthy partner maintains a secured attachment style and doesn't react with anxiety, insecurity, or drama, the person will perceive that as low interest and get bored. Therefore, they will always choose an imbalanced partner rather than a balanced partner.
Note: Those with avoidant or narcissistic traits tend to choose chaotic attachments rather than balanced relationships because it feels more empowering to be with a partner whose emotions are easily triggered by their actions. The avoidant/narc feels validated and empowered when they are able to incite strong reactions of love or hate from their partner. They want their partner to be consumed by them at all times.