Is there a technical reason to now allow closures as the integrand?
 replies(1): 
Integrate supports a variety of numerical integration techniques: - Newton-Cotes methods:
  - Rectangle Rule.
  - Trapezoidal Rule.
  - Simpson's Rule.
  - Newton's 3/8 Rule.
- Gauss quadrature methods:  - Gauss-Legendre.
  - Gauss-Laguerre.
  - Gauss-Hermite.
  - Gauss-Chebyshev First Kind.
  - Gauss-Chebyshev Second Kind.
- Adaptive Methods:  - Adaptive Simpson's method
- Romberg’s method.