Why does the telegram bot see only a part of the conversations in which it was added?

Question

API

Tell me why the telegram bot sees only a part of the conversations to which it was added, and not all?

here is the code to get it:

public function getChats()
    {
        $token = $_ENV['TOKEN'];

        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, 'https://api.telegram.org/bot'. $token .'/getUpdates');
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');

        $headers = array();
        $headers[] = 'Content-Type: application/json';

        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

        $result = json_decode(curl_exec($ch), true);

        if (curl_errno($ch)) {
            return new JsonResponse(['message:' . curl_error($ch)]);
        }

        curl_close($ch);

        $elements = array();
        $chats = [];

        foreach ($result['result'] as $chat) {
            if (in_array(@$chat['message']['chat']['title'], $elements))
                continue;
            else
                $elements[] = @$chat['message']['chat']['title'];

            $chats[] = @$chat['message']['chat'];
        }

        return $chats;
    }

sees approximately 50% of all conversations