Here are some of the key reasons why political representation is not typically structured along racial lines for white people (or any other specific racial group):

Principle of Equality: Basing political representation on race can be seen as contradicting the fundamental principle of equality before the law and equal political rights for all citizens. It could imply that certain racial groups have inherently different interests that can only be represented by someone of the same race, which can be a divisive and potentially discriminatory idea.

Focus on Individual Rights: Modern democratic systems tend to emphasize individual rights and representation. People are seen as individuals with diverse interests and concerns that go beyond racial identity.

Avoiding Racial Division: Creating political representation based on race could exacerbate racial divisions within society by emphasizing racial identity as the primary basis for political organization and action. The goal in many democracies is to move towards a society where race is less politically salient.

Potential for Discrimination: If political representation were based on race, it could lead to the exclusion or under-representation of individuals who do not fit neatly into defined racial categories or who have multiracial identities. It could also create a system where certain racial groups are favored or disfavored in the political process.

Substantive Representation: The focus in contemporary political thought is often on "substantive representation," where elected officials represent the interests and concerns of their constituents, regardless of the representative's or the constituents' racial background. The ability to effectively represent a group depends on understanding their needs and advocating for them, not necessarily on sharing the same racial identity.

However, it's important to acknowledge some related points:

Historical Context of Underrepresentation: Historically, many racial minority groups have faced systemic discrimination and barriers to political participation, leading to their underrepresentation. In some cases, specific measures like affirmative action or the creation of majority-minority districts have been implemented to address this historical disadvantage and ensure more equitable representation. These measures are typically aimed at rectifying past and present inequalities, not at establishing race-based representation as a general principle.

Identity Politics: While formal political structures don't usually organize along white racial lines, white individuals, like any other group, may have shared interests or concerns that lead them to organize politically or support certain candidates. This is part of broader identity politics, where people with shared identities (which can include race, ethnicity, gender, sexual orientation, etc.) may mobilize for political action. However, this is usually distinct from formal, legally mandated political representation based on race.

In conclusion, the absence of political representation specifically for white people stems from the democratic principle of equal individual representation, the desire to avoid racial division and discrimination, and the focus on substantive representation of diverse interests rather than representation based on racial identity.