Tons of composer suggestions after installing...

[Gittinhub]

After running composer install --dev at the directory i unzipped the master.zip, i receive many composer installing suggestions. Why is this? So, why didn't composer install the suggestions? Do i have to install ONE by ONE? How to tell composer to install all of them IF it is needed? It is needed ?
Here goes the packages suggested:
symfony/translation suggests installing symfony/config ()
symfony/security-core suggests installing symfony/validator (For using the user password constraint)
symfony/security-core suggests installing symfony/expression-language (For using the expression voter)
symfony/routing suggests installing symfony/config (For using the all-in-one router or any loader)
symfony/routing suggests installing symfony/expression-language (For using expression matching)
symfony/routing suggests installing doctrine/annotations (For using the annotation loader)
symfony/event-dispatcher suggests installing symfony/dependency-injection ()
symfony/http-kernel suggests installing symfony/config ()
symfony/http-kernel suggests installing symfony/dependency-injection ()
predis/predis suggests installing ext-phpiredis (Allows faster serialization and deserialization of the Redis protocol)
phpseclib/phpseclib suggests installing ext-gmp (Install the GMP (GNU Multiple Precision) extension in order to speed up arbitrary precision integer arithmetic operations.)
phpseclib/phpseclib suggests installing pear-pear/PHP_Compat (Install PHP_Compat to get phpseclib working on PHP < 4.3.3.)
patchwork/utf8 suggests installing ext-intl (Use Intl for best performance)
monolog/monolog suggests installing graylog2/gelf-php (Allow sending log messages to a GrayLog2 server)
monolog/monolog suggests installing raven/raven (Allow sending log messages to a Sentry server)
monolog/monolog suggests installing doctrine/couchdb (Allow sending log messages to a CouchDB server)
monolog/monolog suggests installing ruflin/elastica (Allow sending log messages to an Elastic Search server)
monolog/monolog suggests installing videlalvaro/php-amqplib (Allow sending log messages to an AMQP server using php-amqplib)
monolog/monolog suggests installing ext-amqp (Allow sending log messages to an AMQP server (1.0+ required))
monolog/monolog suggests installing aws/aws-sdk-php (Allow sending log messages to AWS services like DynamoDB)
monolog/monolog suggests installing rollbar/rollbar (Allow sending log messages to Rollbar)
laravel/framework suggests installing doctrine/dbal (Allow renaming columns and dropping SQLite columns.)
phpunit/phpunit suggests installing phpunit/php-invoker (~1.1)
phpdocumentor/reflection-docblock suggests installing dflydev/markdown (1.0.*)
phpdocumentor/reflection-docblock suggests installing erusev/parsedown (~0.7)
barryvdh/laravel-ide-helper suggests installing doctrine/dbal (Load information from the database about models for phpdocs (~2.3))
Writing lock file
Generating autoload files

[Andrew Elkins]

Suggest is just that, suggestions only. They not required. Some packages work well with others. Some package might improve functionality with the suggestions. Composer