I'm a Master Tier subscriber and when I am building a character, I don't have full access to the content. For example, I'm building a lvl 3 Rouge and the only classes I have the option to choose from are Thief and Assassin. Why are Soulknife and Arcane Trickster not presented as options? Why are additional subclasses from source books like Tasha and Xanathar also not available options?

Even though I'm a Master Tier subscriber, do I still need to purchase and own the PHB and other source books to have access to all of the content during character creation?

Quote from dillshea >>

Even though I'm a Master Tier subscriber, do I still need to purchase and own the PHB and other source books to have access to all of the content during character creation?

Yes. Having a subscription does not give you access to any books or character options. You still need to purchase the ones you want to use, or have access to them through content sharing in a campaign.

Quote from dillshea >>

I'm a Master Tier subscriber and when I am building a character, I don't have full access to the content. For example, I'm building a lvl 3 Rouge and the only classes I have the option to choose from are Thief and Assassin. Why are Soulknife and Arcane Trickster not presented as options? Why are additional subclasses from source books like Tasha and Xanathar also not available options?

Even though I'm a Master Tier subscriber, do I still need to purchase and own the PHB and other source books to have access to all of the content during character creation?

 https://marketplace.dndbeyond.com/subscribe#tiers-comparison-table

"Share purchased content", not "Access everything we have for a tiny fraction of it's cost."

Also in the FAQ on that page:

Are any books included in my subscription?

Books are not included at any subscription level, and they must be purchased through the D&D Beyond Marketplace to access their digital features. However, the Free Rules are available to all players.