INTJs, also known as the "Architects" or "Masterminds," are known for being one of the most private and reserved personality types. They often do not openly express their true personalities for several reasons:

1. Self-protection: INTJs are highly self-aware and value their privacy. They tend to be cautious about revealing their true selves to others, as they fear being misunderstood, judged, or taken advantage of. They prefer to keep their thoughts, emotions, and vulnerabilities hidden to protect themselves from potential harm.

2. Analytical nature: INTJs have a strong analytical and logical mindset. They tend to approach situations and interactions with a rational and objective perspective. This analytical nature often leads them to carefully observe and assess others before revealing their true selves. They prefer to gather information and understand people's intentions before opening up.

3. Fear of rejection: INTJs have a deep fear of rejection or being seen as incompetent. They often strive for perfection and can be highly critical of themselves. This fear can make them hesitant to show their true personalities, as they worry about being judged or not meeting others' expectations.

4. Selective disclosure: INTJs are selective about who they choose to reveal their true selves to. They prefer to establish trust and build a strong connection with someone before opening up. They value depth and authenticity in relationships and tend to keep a small circle of close friends who they feel comfortable being themselves around.

5. Focus on efficiency: INTJs are highly goal-oriented and focused on efficiency. They may prioritize achieving their objectives over expressing their true personalities. They often see small talk or socializing as distractions and prefer to invest their time and energy in activities that align with their long-term goals.

6. Emotional reserve: INTJs are not naturally inclined to express their emotions openly. They tend to keep their emotions under control and may find it challenging to articulate their feelings. This emotional reserve can make it difficult for others to understand their true personalities, as they may come across as detached or unemotional.

It is important to note that while INTJs may not openly show their true personalities, it does not mean they are being deceptive or hiding something negative. They simply have a preference for privacy and take time to trust and reveal themselves to others. Building a strong connection and demonstrating understanding and respect can help an INTJ feel comfortable enough to share their true selves.